Jake Gyllenhaal did not receive an Oscar nomination for portraying Capt. Colter Stevens often as Sean Fentress in Source Code.
We first meet Jake Gyllenhaal in the film as a man on a commuter train. Gyllenhaal's performance begins as a proxy for the audience as the man attempts to figure out why he's on a train, and what exactly is going on. Gyllenhaal is effective jumble of thoughts as the man attempts to gain his bearings which are difficult to obtain when he sees someone else's reflection in the mirror, and the train he's riding on explodes only a few minutes later. The man wakes up to find himself in an odd chamber where he is told by a military operative (Vera Farmiga) that he is being used to essentially quantum leap into another man's body in the past in order to discover the source of a terrorist attack. Gyllenhaal's performance works well here as he manages to give reality to the concept immediately by portraying such paranoia in the task, and such confusion as he wonders how exactly he ended up with the task in the first place. Gyllenhaal's own task in the role is to keep up with the film as it continues at a fairly rapid pace as the soldier Colter Stevens keeps getting sent back into the man Sean Fentress in order to find who set the bomb that blew up the train.
Stevens's "handlers" constantly push him to stay on task despite his myriad of questions especially after he learns from a news report in the past that Stevens also has been declared dead. Gyllenhaal basically must constantly be switching intents as Stevens still goes about trying to solve the mystery while trying to attempt some sort of personal closure as well. Gyllenhaal maneuvers this firm pace rather flawlessly as he goes from either in Fentress as he narrows down suspects to Stevens who is kind of broken due to learning about his state. When Stevens "plays" Fentress there is not even a single set manner that Gyllenhaal establishes. Gyllenhaal instead succeeds in matching whatever he needs to be given Fentress's situation in the past. Gyllenhaal importantly never loses the sense of severity as he searches for answers, though he does well to convey a proper variation of it depending on the moment. Whenever he's reminded of the loss of life when he knows that the explosion is about to happen Gyllenhaal gives it the necessary gravity.
Gyllenhaal is never one note as just a hysterical man finding a bomb or a terrorist, even though he does that quite well when it is asked of him as well. Gyllenhaal again plays the part of Fentress in a way and does so brilliantly. This even includes a rapid fire romance with the woman Christina (Michelle Monaghan). Gyllenhaal whips out a bit of required charm for this and makes it convincing, though one should also note Monaghan certainly helps a lot by portraying Christina as being infatuated with Fentress from the beginning. Gyllenhaal is equally efficient in transitioning to the man who will do what it takes to get the job done. Gyllenhaal manages to bring the proper intensity and even menace as he goes about interrogating a few of the passengers to find the culprit. There's even a bit of humor that Gyllenhaal effortlessly find from time to time just within the awkwardness of this man attempting to be so many things at once, I particularly enjoy his false bravado when he pretends to be a train marshal by using a regular wallet.
The final element of Gyllenhaal's performance is when Stevens is in the "chamber" and when he is directly attempting to cope with his bizarre physical state. Gyllenhaal is rather moving by depicting the strange agony. This again is all in rapid succession of one another yet Gyllenhall's portrayal of any of these sides never feels vague or underwhelming. This all culminates to a final trip to the past as Stevens attempts to live a perfect final eight minutes, basically pulling off the last day of Groundhog's day. Gyllenhaal just exudes such a earned confidence as he owns scene while Stevens own the situation. Gyllenhaal presents a man in absolute control of everything in the moment and it is wonderful to watch him basically make the absolute best of his final minutes. This includes one powerful moment when he calls his father. Gyllenhaal infuses such poignancy to the conversation as honestly portrays finally gaining a certain sense of closure as Stevens says his goodbye. Gyllenhaal is outstanding as he builds to the final bittersweet ending of triumph by achieving all he could with his remaining time. The film for some reason goes on, but hey that's hardly Gyllenhaal's fault. This is a very strong performance by Jake Gyllenhaal which is pivotal to the film's success. He not only is an endearing leading man, but keeps its core concept grounded in a very human reality.