OXNARD, Calif. — The third-team quarterback is guiding his unit down the field in team drills Sunday, closing in on the goal line but running out of time according to the end zone clock. A fan shouts, “Let’s go Trey, shake the rust off …’’ Rust, indeed. Trey Lance, the mystery acquisition the Dallas Cowboys made 11 months ago, is perhaps the mystery man of the entire NFL. The quarterback selected with the third pick of the 2021 draft by the San Francisco 49ers — does he still possess the potential that made Kyle Shanahan and John Lynch trade three first-round picks to move up to get him?The Cowboys think so, or at least management does. Otherwise, they would not have sent a fourth-round pick to the 49ers a year ago for a guy who has barely dipped his toe into the NFL waters. But trading for him when they did (right at the end of preseason), the Cowboys never got to use him in an August game and Lance did nothing more than direct the scout team in practice and dress as the No. 3 quarterback for every game last season.So now he is here, throwing passes and ... getting stopped at the 1-yard line as the clock ran out Sunday. Who is he? What is he? Everyone wants to know, not just because of the curiosity that comes with having been such a high pick. The Cowboys have a little decision to make on Rayne Dakota Prescott, 31 years young as of Monday, and while logic says the Cowboys will extend him at some point, at that level of money (at least $60 million per season), there are no givens.So who is Trey Lance? He’s not a bust because he hasn’t played enough to be declared anything of the type, not like Denver’s Zach Wilson who was almost reviled by Jets’ fans for his play and occasionally his attitude. Wilson was picked one spot ahead of Lance. Trevor Lawrence went with the first pick and already has been rewarded with a second deal averaging $55 million per year, so at least the Jaguars have decided Lawrence is the real deal even if others are less certain.With Lance, as a rookie with the 49ers he mostly watched Jimmy Garoppolo but he came off the bench a few times and made two starts. Twice his first pass of the game ...