"I can handle this," Mulder wrote on his Twitter account, @markmulder20, shortly after receiving the MRI results. "But seeing my son in tears when he saw me in a boot and crutches and I told him I wasn't going to pitch - that was tough."
The injury -- the same one Ryan Howard suffered while making the last out of the 2011 National League Division Series -- will require surgery and typically takes months to recover from. Given Mulder's age (36), his no-strings-attached Minor League contract and his general acceptance of being away from the game, he'll probably opt for a return to retired life.
"My heart goes out to him," said Angels general manager Jerry Dipoto, who didn't want to speculate on what decision Mulder would make about his future. "I know how hard he worked, and we're all disappointed for him. Every one of us."
Mulder is expected to address the media from Angels camp on Sunday morning.
Prior to that, the left-hander talked openly about how good his arm felt and how ready he was to attempt a comeback few have ever completed.
It started in October, when Mulder was watching Dodgers reliever Paco Rodriguez pitch in the playoffs, stood up in his living room, mimicked a quicker, more fluent delivery, translated it to the pitching rubber and came away amazed by how much better it made him throw.
"I haven't had the ball come out of my hand like this in a very long time," Mulder said over the offseason, "and it's fun."
He dazzled in a late-November bullpen session and hooked on with the Angels on an incentive-laden contract that would pay him anywhere between $1 million and $6 million if he made the Major League roster. Then, shortly after the New Year, Mulder made sure his arm could stand up to the rigors of being a starting pitcher by engaging in two 100-plus-pitch simulated games, followed by 40-plus-pitch bullpen sessions twice a week leading up to Spring Training.
Mulder noticed gradual improvement, both with his stuff and his command, every time he stepped on the mound.
Eight days ago, everything clicked.
"That was the first day I really thought to myself, 'OK, I'm ready to start this,'" Mulder said Friday.
The following morning, he sustained what's probably a season-ending ankle injury during a change-of-direction warm-up drill at one of the back fields of the Tempe Diablo Stadium complex, minutes before throwing his first bullpen session in front of Angels coaches.
The Angels weren't necessarily counting on a Mulder comeback, so his injury isn't expected to intensify their pursuit of outside starting pitching help. Tyler Skaggs, 22, is still the favorite for the fifth spot in the rotation, but Joe Blanton's importance has suddenly heightened as a potential fallback option.
The Angels are still not expected to sign any starters to a Major League contract, especially guys like Ubaldo Jimenez and Ervin Santana, who are tied to Draft-pick compensation.
Mulder was the second overall pick by the A's in the 1998 First-Year Player Draft and established himself as one of the game's premier left-handers over a five-year period, averaging 18 wins and posting a 3.65 ERA from 2001-05. But he pitched only 12 2/3 innings with the Cardinals from 2007-08, a product of two rotator cuff surgeries, and moved on immediately thereafter, briefly trying his hand at professional golf before becoming an ESPN analyst.
His attempt at a comeback was the result of an epiphany, not the necessity to fill a void.
"I don't know what's going to come of it," Mulder said previously, "but I just know that I'm very confident in what I'm doing, and I'd like to think that when the Angels people see me throw, I'm going to hopefully turn some heads."
Mulder never got that chance.