Mara became Juror No. 1 on Thursday in the second week of a major international drug case. He was elevated after another juror got sick from possible food poisoning. It was unclear if Mara might become jury foreman.
Mara had tried to escape being seated on the trial last week, saying he had to prepare for next week's NFL draft. He also cited responsibilities as a negotiator for team owners in the NFL's work stoppage.
He was an alternate until he was promoted after lunch Thursday, his sixth day on the jury. The trial is likely to last another two weeks.