USC QB Sam Darnold

Biggest strengths: I love Darnold's playmaking ability, toughness and his durability. He has a clutch factor, too. He's made some big-time plays over the last two years. His intangibles are off the charts. Darnold's a big, sturdy QB and he can make every throw.

Biggest question mark: Turnovers were a huge issue for Darnold this season. Sometimes when you have as many fumbles as Darnold did this season (11), it leads to concerns about hand size, and with the teams holding the top two picks -- Cleveland Browns and New York Giants -- playing in cold-weather environments late in the season, hand size is a particularly important factor they consider when evaluating QBs. People want to know how big his hands are, and that will be something to watch for when he's measured at the NFL Scouting Combine.

UCLA QB Josh Rosen

Biggest strengths: You're going to hear this a lot between now and April -- Rosen is the best pure passer among draft prospects. In fact, he's the most talented passer by a good margin. From a footwork and release standpoint, it's beautiful to watch him throw. It's a bonus that he's spent a good amount of time under center in a pro-style offense, as well.

Biggest question mark: Durability. He's missed several games over the past two seasons. Teams will weigh that heavily as they evaluate him. The other thing to watch is how teams think his personality will fit inside their building. He's caught a lot of heat for being outspoken with the media, but I think clubs are more interested in what he's like behind the scenes. Clubs are going to want to spend a lot of time getting to know him.

Oklahoma QB Baker Mayfield

Biggest strengths: The combination of accuracy and energy Mayfield brings to the game is unique. He has plenty of arm strength, as well as a knack for making big plays. I don't think he'll blow people away with his testing at the combine, but he's a good athlete. He's very instinctive.

Biggest question mark: How tall is he? Mayfield is listed at 6-foot-1 by Oklahoma, but we'll get an official measurement on him later this month when he attends the Reese's Senior Bowl. He'll be the most anticipated weigh-in guy at an all-star game since Russell Wilson in 2012. There were questions about Wilson's height when he was entering the draft, which led to a lot of intrigue when he was measured at the Senior Bowl. We know how things worked out for the Seahawks QB. There will be a buzz when Mayfield's height is measured at the same event later this month. The other big question for Mayfield has to do with character. I don't think teams will be bothered much by some of his on-field antics, but he'll have to answer for his arrest from last February.

Wyoming QB Josh Allen

Biggest strengths: Allen has the highest upside of any QB in the class. He has a rare combination of his size, arm strength and athletic ability. I think Allen is the best athlete of these four QBs.

Biggest question mark: Will he play winning football against top competition? Allen has the highest ceiling, and the lowest floor of the bunch. The biggest knock on him is his play against top-level opponents. He has a career TD-INT ratio of 1-8 in his three career games against Power Five teams. He would have a great opportunity to show what he's capable of against top competition if he plays in the Senior Bowl.