That's when Kyler Murray -- the Cardinals' No. 1 overall pick in the 2019 NFL draft -- publicly announced his intention to play professional football instead of professional baseball.
For months, the Cardinals toyed with Rosen. And Friday night, when the trade to send Rosen to Miami was official, marked the end of a grossly mismanaged situation that botched what could've been a seamless divorce.
It had little to do with Rosen, despite a dismal rookie season that included a miserable 3-13 record, but a lot to do with Murray. When the Cardinals hired Kliff Kingsbury as their coach, he brought with him a revolutionary offense and a long-time relationship with the reigning Heisman Trophy winner.
The day Murray decided to pursue football was the day the Cardinals decided to make him the No. 1 pick.
A day after, Kingsbury declared that "Josh is our guy." But that, as it turned out, was Rosen's kiss of death.
Rosen never had a chance of standing between Kingsbury and Murray.
"As the evaluation went on ... it became evident that we felt like Kyler was a special talent, that he was the best player in the draft and we had to take him," Kingsbury said Friday night, after Rosen was traded to the Miami Dolphins for a second-round pick this year and a fifth-round pick next year.
Rosen could've had the best touchdown-to-interception ratio of any rookie QB last season, could've put up big numbers, but it probably wouldn't have mattered. He still most likely would not have been the Cardinals' quarterback in 2019.
Kingsbury was already raving about Murray, whom he began recruiting in 2012 out of Allen High School in suburban Dallas, at the combine. It was around then -- late February into early March -- that Cardinals general manager Steve Keim began listening to offers for Rosen.
Why listen to offers if the idea to draft Murray wasn't already being seriously considered?
On Friday, Kingsbury said he would've been excited to work with whoever was in the quarterback room next season, and Keim said the decision to trade Rosen had as much to do with the value of the trade as anything, yet the trade only really benefited the Cardinals one time -- with the 62nd pick -- this year. It was a foregone conclusion for months that the Cardinals were drafting Murray, yet they kept dragging Rosen along, continuing to say they trusted him with the offense and praising him as a professional, a person and a player.
Rosen left town graciously, but in private, he was getting frustrated with the constant chatter about his future. And rightfully so.
The Cardinals had decided to hand the franchise to a 21-year-old phenom, instead of staying the course with a 22-year-old whom they traded three picks to get in 2018. The Cardinals' QB decision was solidified on Friday night, another date now etched in stone in the story of Rosen's tenure in Arizona.
It was the date that Rosen was officially made the past and Murray officially given the future.