Here’s a closer look at what they accomplished this season, plus what they need to improve upon for next season:
Stat line: 12 games (11 starts), 169-for-320 (52.8 percent) for 2,074 yards, 10 touchdowns and 12 interceptions; 89 rushes for 631 yards and eight touchdowns; 67.9 passer rating; 52.0 Total QBR
Season-defining play: Allen's 75-yard touchdown pass to Robert Foster during a Week 12 win over the Jaguars. Allen made many of the best plays of his rookie season with his legs or when throwing on the run, but the most promise he showed as a pocket passer came when he launched a pass 39 yards in the air despite being sandwiched by two Jaguars pass-rushers. Allen has an obvious talent to effortlessly flick passes with eye-opening velocity and distance. This play showed he could do that accurately while standing in the pocket against pressure.
They said it: “You saw the difference in a lot of how things slowed down from Josh’s first [games as the starter] prior to [his Week 6 elbow] injury to when he came back [in Week 12]. He was definitely more comfortable, for the most part. He’s still got a ways to go. He [was] a rookie. He’s not arrived by any means.” -- Bills general manager Brandon Beane
What's ahead: The Bills will spend their offseason trying to build up their offense around Allen, particularly along the offensive line and at pass-catcher, in an effort to take Allen's game to the next level. Buffalo has publicly committed to LeSean McCoy for the final season of his contract in 2019, but the Bills will need their running game to step up to take pressure off Allen. The rookie was only the fourth quarterback this century to lead his team in both passing and rushing, something the Bills do not want to continue. -- Mike Rodak
Stat line: 13 games (13 starts), 239-for-414 (57.7 percent) for 2,865 yards, 17 touchdowns and 15 interceptions; 44 rushes for 189 yards and one touchdown; 77.6 passer rating; 48.4 Total QBR
Season-defining play: Darnold’s 7-yard touchdown pass to Robby Anderson in Week 14 showed the entirety of his skill set. Under pressure, he escaped the pocket to his right, changed direction with a spin move, scrambled across the field and fired a tight-window pass to Anderson in the end zone. All told, he scrambled 48 yards, according to NFL NextGen Stats. The play demonstrated Darnold’s athleticism, field awareness and accuracy on the run -- his strongest traits.
They said it: “I truly believe that this kid is going to be a star. He just keeps getting better. Big picture, this organization and this fan base have a lot to look forward to with this guy.” -- Jets wide receiver Jermaine Kearse
What’s ahead: Darnold’s first priority is to learn coach Adam Gase’s system. To accelerate the process, he’s planning to study Dolphins video from the 2018 season. Once he gets on the field, Darnold needs to cut down on his interceptions -- 15 is too many for 13 starts. The good news is he had no interceptions in the final 13 quarters, which should make for a good springboard into 2019. Darnold's field vision improved considerably over the final four games, which allowed him to lead the NFL in Total QBR (80.7) in that span. -- Rich Cimini
Stat line: 17 games (eight starts, including playoffs); 99-of-170 (58.2 percent) for 1,201 yards, six touchdowns and three interceptions; 147 rushes for 695 yards and five touchdowns; passer rating: 84.5; Total QBR: 45.4
Season-defining play: With a playoff berth on the line, Jackson answered the Ravens' first deficit to the Browns by running 25 yards for a score. This year's leading rusher among quarterbacks, Jackson kept the ball on an option on third-and-4 and ran up the middle untouched in the first quarter. The Ravens' longest touchdown run of the season helped Baltimore to a 26-24 win over Cleveland and showed once again why Jackson was the Ravens' most explosive playmaker.
They said it: "He is the future. He’s such a bright kid, unbelievable energy and personality. He’s likable. He works hard. He’ll come back 10 times better than he was this year. For what he did, and to the belief that he gave not only our team but our city, this organization, is pretty special.” -- Ravens safety Eric Weddle
What’s ahead: The Ravens will go with Jackson as their starter in 2019 and part ways with Joe Flacco this offseason (either by trade or release). For Jackson to take the next step, he has to improve his accuracy and ball security. He struggled in driving the ball downfield, especially when trying to hit receivers along the sideline. He was 33-of-69 (47.8 percent) when throwing outside the numbers, which was the worst completion rate among quarterbacks with at least 50 such attempts. Holding onto the ball was another issue. When you count the three fumbles in the playoff loss to the Chargers, Jackson totaled 13 in his eight starts (he fumbled twice before he became the starter). That projects for 26 in a full season as a starter, which would set an NFL record. -- Jamison Hensley
Stat line: 14 games (13 starts); 310-for-486 (63.8 percent) with an NFL rookie-record 27 touchdowns and 14 interceptions; 39 rushes for 131 yards and no touchdowns; passer rating: 93.7; Total QBR: 55.7
Season-defining play: Although it went for only 2 yards, it provided the winning points against Denver, and this play showed Mayfield’s growth running the offense, recognizing mismatches, getting players in the right spots and managing the game. In a sense, that's Quarterback 101 in the NFL, but for a 23-year-old rookie in a tough environment, it’s not always easy. This play involved Mayfield trying to rush a snap to keep the Broncos from substituting, returning to the huddle to rush through the playcall, lining up, recognizing that Antonio Callaway had a safety on him outside, changing the play to a slant and physically moving Duke Johnson for protection. Mayfield got it done and completed the winning touchdown.
They said it: “He started out, and he was not really highly recruited. He ended up at Texas Tech, but he was not a highly recruited guy, and he found a way to succeed there. He found a way to make his way to Oklahoma to succeed there. He has worked for everything he has ever gotten. Nobody has ever given him anything. That is why I like him. I like those guys that fight and claw for everything they get, and that is what he is. I don’t think he is ever going to be settled.” -- Browns coach Freddie Kitchens
What's ahead: At long last, there is reason for optimism in Cleveland. Mayfield’s play, attitude, competitiveness and approach bode well for the future, especially with Kitchens staying as head coach after he developed a great rapport with Mayfield as the interim offensive coordinator. The Browns are betting on this pairing for the future, and both the principals provided sound reason for doing so and sound basis for believing that good days are ahead for the Browns. -- Pat McManamon
Stat line: 14 games (13 starts); 217-for-393 (55.2 percent) with 11 touchdowns and 14 interceptions; 23 rushes for 138 yards and no touchdowns; passer rating: 66.7; Total QBR: 25.9
Season-defining play: The Cardinals were at their own 13 facing third-and-23 with 4:35 left in a tied game at Green Bay on Dec. 2. Rosen was patient in the pocket as the play developed, which as the season went on became his best quality. When the pocket collapsed, Rosen was flushed to his right, waved a couple players open and fired a strike to Larry Fitzgerald for a first down. That led to the game-winning field goal.
They said it: “I’ve seen Josh progress. I know this is an ongoing question because the record, the stats, don’t show, but I think he’s getting certain looks where he’s improving.” -- former Cardinals head coach Steve Wilks
What's ahead: Rosen will have his second head coach and third offensive coordinator in two seasons, with Kliff Kingsbury replacing Wilks as head coach. The jury is still out on how Kingsbury, who coached Texas Tech’s offense to be one of college football’s most prolific, will help an NFL quarterback. The game is different, even if some collegiate schemes have made their way to the pro game. -- Josh Weinfuss