Baker Mayfield began the 2015 college football season as one of the strongest contenders for the Heisman Trophy, but the Oklahoma quarterback finished the year on a sour note, with his worst game of the season coming against Clemson in the College Football Playoff.

Mayfield was outstanding for most of the season, however, and should be just as good in 2016. So what went wrong for the quarterback against Clemson, and what makes him so good that he's likely to bounce back? Let's take a look.

Too many mistakes against Clemson

One thing that was key to Mayfield's success last year was that he didn't make a lot of mistakes. In fact, before the game against Clemson, he had just four passes where we gave him a grade or -1 or -1.5. Those are the throws that are generally turnover-worthy, so the fact that he had just four of them in 455 passing attempts is pretty incredible.

However, Mayfield then posted three such throws against Clemson alone. Forced throws, misreading coverage, bad enough under-throws to be picked off — the type of mistakes he just didn't make during the regular season.

This throw came on 1st-and-goal with 7:32 left in the game, with Clemson up 37-17. While there was an element of forcing things to chase the game, it was still the type of throw that we've seen so rarely from Mayfield. His -1.5 passing grade in the game was the lowest he produced all season, and he struggled under pressure, completing just six of the 11 passes he attempted. He also struggled throwing the ball downfield, completing just two of the eight throws of 20 yards or more he attempted.

It was a poor game from Mayfield — there's no doubt about that, but what we saw from Mayfield over the course of the 2015 suggests that he'll absolutely bounce back from that game, and comes into the 2016 season as the best quarterback in the nation.

The best returning QB in the nation?

It was a poor game from Mayfield, there's no doubt about that, but what we saw over the course of the season suggests he'll absolutely bounce back — perhaps as the best college quarterback in the country?

To compare, Matt Johnson and Jared Goff were the only two QBs last year who had a higher overall grade than Mayfield's +49.6 score. The issues against Clemson game were limited to that game, and while he graded higher without pressure than under pressure, he still had a +4.0 grade over the course of the season when pressure got there. There were no struggles throwing the ball downfield either, with Mayfield completing 27 of the 60 passes 20 yards or more downfield he attempted.

An outstanding downfield passer, he threw 11 touchdowns and no interceptions on downfield throws. The most impressive of these is shown in the clip above against Baylor, as he hits his receiver perfectly in stride for the touchdown.

Through the air and on his legs

As much as Mayfield's arm is his best weapon, he graded well as a runner, too. At +8.3, his rushing grade was the 21st-best among quarterbacks in all of college football last year, with Mayfield rushing for 598 yards, scoring seven touchdowns and forcing 23 missed tackles. 48 of his runs came on quarterback scrambles, and this was where he did some of his best work. He ran for 386 yards on those scrambles, forcing 16 missed tackles and scoring three touchdowns.

He wasn't purely a scrambler, with the Sooners able to build some designed runs from him into their offense. On designed runs off left end Mayfield has the most success, rushing for 113 yards on 18 attempts. It's important that he's good enough be used on the ground as well, and it's a big part of why he's so successful.

Mayfield is the perfect all-round quarterback for a college system like Oklahoma. He has the arm to make big-time throws downfield, is smart enough to limit mistakes, and has the athleticism to create big plays with his legs.

The game against Clemson was a disappointing end to what was a spectacular season, but when one takes a look at the bigger picture, it's obvious the game was a minor blip in terms of how Mayfield is viewed as a player. He comes into the season as a Heisman Trophy contender and arguably the best quarterback in the nation — and if his 2015 performance is anything to go by — he can drive the Sooners towards the College Football Playoff once again.