Entering the 2015 season, had plenty of doubters and had none. Through Week 4, one quarterback has accumulated a 123.0 pa ser rating and a 9:1 touchdown-to-interception ratio while leading his team to a 4-0 record, while the other trails the league in pa ser rating and has notched just one win as a starter. Before the season began, who would've gue sed Dalton would be the former and Luck would be the latter?Surprises abound in every NFL season, but the "unexpected narrative" bug seems to have hit the quarterback position especially hard this year. So I've decided to examine three quarterbacks who are enjoying eyebrow-raising succe s (two veterans outpacing their career pa ser ratings by at least 20 points, plus one outstanding rookie) and three quarterbacks enduring curious struggles (posting pa ser ratings at least 16 points below the norm), to see if these unexpected starts are for real or not.THREE QBS Mark McGwire Jersey OUTPERFORMING EXPECTATIONSAndy Dalton, Cincinnati Bengals2015 stats: 67.2 percent completion rate, 1,187 yards, 9 TDs, 1 INT, 123.0 pa ser rating (through four games).On pace to finish with: 4,748 yards, 36 TDs, 4 INTs.Career stats entering 2015: 61.6 percent completion rate, 3,690 yards per season, 25 TDs per season, 16 INTs per season, 85.2 pa ser rating.My feeling on Dalton has changed. Two weeks ago, while recognizing that he and the had played well in jumping out to a 2-0 start, that the quarterback wasn't a true game-changer, someone who could be trusted to push the to new playoff heights. But since then, Dalton's shown guts, making late in a tough win over the and against the . His pa ser rating is easily dwarfing what he's done before -- his previous career high was 88.8 in 2013 -- and I think he'll continue to play at a high level going forward. The fact that he has a dynamite supporting cast can only help. Is this for real? Yes. We've seen good stretches from him previously, especially early in seasons, but it looks to me like Dalton has reached another level, playing with more confidence than ever. Consider that he's posted a 100-plus pa ser rating in four consecutive games for the first time in his career. He's also upped his yards-per-attempt mark considerably, from a career average of 7.0 entering 2015 to 10.2 this season. My concerns have been a suaged, and I see him finally shedding his label as someone who struggles in big spots.Marcus Mariota, Tenne see Titans2015 stats: 62.9 percent completion rate, 833 yards, 8 TDs, 2 INTs, 109.2 pa ser rating (through three games).On pace to finish with: 4,443 yards, 43 TDs, 11 INTs.Mariota is having an unbelievable start to the season. In addition to the gaudy numbers he's piled up thus far, he has the scoring 29.7 points per game, in the NFL. He's been phenomenal. He knows where to throw the ball. He can read the defense. He runs when it's nece sary to run. He was supposed to need time to acclimate to the pro game, but he's surprised everyone, seemingly knowing how to do the right thing at the right moment from Day 1.Is this for real? My eyes say, 'Yes,' but history says there's no way in heck he can continue at this pace. Rookie quarterbacks simply aren't supposed to be this good right out of the gate. completed 55 percent of his pa ses in his first three NFL games, with a touchdown-to-interception ratio of 3:8 over that span. John Elway started 10 games as a rookie and finished with a completion rate of 47.5 percent and a pa ser rating of 54.9. Yes, other rookie quarterbacks have finished with 100-plus pa ser ratings in recent years, like (102.4, still the highest by a rookie) and (100.0) in 2012, but Mariota has been throwing at a much higher rate than either of those players did -- Mariota has attempted 32 pa ses per game thus far and is on track to throw for 4,000-plus yards, much more than both Griffin (26 attempts per game, 3,200 yards) and Wilson (25 attempts per game, 3,118 yards). The only two rookies in NFL history to top the 4,000-yard mark are in 2011 and in 2012, and both finished with much lower pa ser ratings (84.5 for Newton, 76.5 for Luck).Can Mariota be the outlier Sonny Gray Jersey ? It's worth noting that if you exclude his perfect pa ser rating (158.3), his pa ser rating over his past two games (89.7) is more in line with Newton's and Luck's, though it's still high. We'll see what happens as defenses continue to adjust to him. Carson Palmer, Arizona Cardinals2015 stats: 63.4 percent completion rate, 1,155 yards, 10 TDs, 3 INTs, 106.4 pa ser rating (through four games).On pace to finish with: 4,620 yards, 40 TDs, 12 INTs.Career stats entering 2015: 62.6 percent completion rate, 3,215 yards per season, 20 TDs per season, 14 INTs per season, 86.3 pa ser rating.Entering 2015, Palmer's pa ser rating hadn't reached triple-digits since the 2005 season, his second with the , which famously ended with . He bounced back in 2006 with a pa ser rating of 93.9 but the 80s remained his firm ceiling for the rest of his tenure in Cincy. In 2011, I think then- coach Hue Jackson saw Palmer for the top-notch quarterback he was, which is why he . Now that Palmer's in Arizona and healthy after last season, he's playing at a higher level than I've ever seen him play. Palmer has Dan Marino-like instincts; it's like he has a camera on his back that lets him know when Dennis Eckersley Jersey to step away and when the rush is coming. He has an excellent team around him -- especially receivers and -- and a knack for throwing the ball where only his guy can make a play on it.Is this for real? Yes. He's 35, but I think he's reached the point where he's simply on top of his game. I think a sistant Tom Moore -- who helped for so long in Indianapolis -- does such a good job preparing his quarterbacks mentally. Palmer's pa ser rating might drop a bit, but he'll finish in triple-digits, provided he stays healthy, and give the a good shot at being a team.THREE QBS UNDERPERFORMING EXPECTATIONSColin Kaepernick, San Francisco 49ers2015 stats: 62.1 percent completion rate, 727 yards, 2 TDs, 5 INTs, 67.7 pa ser rating (through four games).On pace to finish with: 2,908 yards, 8 TDs, 20 INTs.Career stats entering 2015 (since becoming a starter in 2012): 60.1 percent completion rate, 2,793 yards per season, 17 TDs per season, 7 INTs per season, 90.7 pa ser rating.I don't know if I've ever seen a quarterback with Kaepernick's list of accomplishments perform so poorly in the first four games of a given season. He -- and he to the the following season. Through four weeks in 2015, Kaepernick appears to have fallen off a cliff, compiling a putrid TD-to-INT ratio (2:5) while leading (12 points per game) in the NFL. He's never been the most accurate pa ser in the world, but he used to at least make big throws, which he's not doing this year -- his yards-per-attempt mark has dropped from 7.5 entering 2015 to 6.3 this season. He's also getting sacked more than ever before, with his sack percentage climbing to a career-high 10.8 in 2015. In all probability, defenses have adjusted to him. I also suspect a lack of organizational stability last season -- with the way coach Jim Harbaugh's tenure in San Francisco -- played a role in hampering his development.Is this for real? Yes; I think he's going to have a hard time turning his season around. But he's definitely salvageable as an NFL quarterback. He's demonstrated arm strength and mobility over the course of his career, and he is, for what it's worth, on track to finish with a career high in rushing yards (780). He's also had considerable succe s before. And I think offensive coordinator Geep Chryst is pretty good. So there's hope, provided his mentality is right. Andrew Luck, Indianapolis Colts2015 stats: 56 percent completion rate, 753 yards, 5 TDs, 7 INTs, 65.1 pa ser rating (through three games).On pace to finish with: 3,765 yards, 25 TDs, 35 INTs.Career stats entering 2015: 58.6 percent completion rate, 4,319 yards per season, 29 TDs per season, 14 INTs per season, 86.6 pa ser rating.After three consecutive seasons of continued improvement, Luck has taken a shocking nosedive, posting a pa ser rating that ranks as the worst in the NFL through Week 4 and throwing seven picks, tied for the most in the league. He's making mistakes we haven't seen him make recently, bouncing throws to guys and showing poor accuracy; it's like he has something on his mind other than football. He's been blitzed a lot behind a struggling offensive Stephen Piscotty Jersey line, and he's been sacked five times, which could be causing a dip in performance, since he doesn't have as much of a chance to set his feet. And the lack of a running game has also hurt. But then again, Luck dealt with a poor O-line and run game last season, and that didn't stop him from shining (4,761 yards, 40 touchdowns, 16 picks) en route to the AFC title game. This season, his team is 2-2 -- and he wasn't even on the field for the ' , suffered .Is this for real? This is a mystery to me and, I think, to a lot of people. Suddenly, he has a hill to climb. He'll improve on what he's done to this point -- he's too talented not to -- but I don't know if he's going to fulfill my expectations for what he could have done this season. I don't believe he'll stick to his outlandishly bad pace; he should finish with a better TD-to-INT ratio, a completion rate in the 60-percent range, a healthier yards-per-attempt mark and a pa ser rating in the 80s. But entering this season, I had him up there in territory -- and those aren't "second to " numbers. Now he's already mi sed one game and by the team ahead of with the . that has surrounded the can't help; that kind of stuff can Terry Steinbach Jersey affect the whole team.I'm confident Luck will still be a top-five quarterback five years from now; I have no doubt about that. But it looks like he's going to continue to underperform expectations in 2015.Peyton Manning, Denver Broncos2015 stats: 63.6 percent completion rate, 968 yards, 6 TDs, 5 INTs, 80.8 pa ser rating (through four games).On pace to finish with: 3,872 yards, 24 TDs, 20 INTs.Career stats entering 2015: 65.5 percent completion rate, 4,099 yards per season, 31 TDs per season, 14 INTs per season, 97.5 pa ser rating.Manning is a 39-year-old who's been in the NFL since 1998 -- so it's not shocking that his numbers have taken a dip. Still, he was performing at an extraordinarily high level as recently as last season. And it was only two years ago that he set the single-season record in pa sing yards (5,477) and pa sing touchdowns (55). From 2012 to 2014, he completed 67.7 percent of his pa ses for 14,863 yards, 131 touchdowns and just 36 picks -- that's pretty darn good. One of the most noticeable declines this season has come in his yards-per-attempt mark, which has shrunk from 8.1 over the past three seasons to 6.3 in 2015. Plus, he's on pace to finish with more picks (20) than he's thrown since 2001 (23). He's not throwing the ball as far downfield, and he's probably not putting as much velocity on the ball as he once did.Is this for real? Yes. He might improve a bit over the next few weeks, especially now that the have put him in the pistol, but I think as the season wears on and it gets more difficult to throw outdoors, he'll regre s back to around the level we've seen him at thus far. I expect him to finish with a pa ser rating in the 80s, which he hasn't done since 2002; if it stays close to 80, it could be his lowest pa ser rating since he posted a 71.2 as a rookie. But Manning is still the same well-prepared guy he's always been, and he has two great receivers in and catching pa ses for him. So I don't see him getting much worse. And that's good news for Denver. Because the bottom line is, the are 4-0, and their Wade Phillips-led defense gives them a good chance to win in the playoffs -- even with Manning operating at this level. Follow Gil Brandt on Twitter __.