In Game 3, it started to become obvious that the partial tear of the labrum in Lowell's right hip was limiting him to the point that even the most routine baseball activity was a chore.
The Red Sox added utility infielder Gil Velazquez -- a veteran Minor Leaguer -- to the roster to replace Lowell. The 28-year-old Velazquez has played three games in the Major Leagues, all with the Red Sox over the final days of this season.
As far as starting options, Mark Kotsay was in the starting lineup at first base in Game 4 with Kevin Youkilis moving across the diamond to third.
Red Sox manager Terry Francona has other options going forward as well, such as keeping Youkilis at first, moving shortstop Jed Lowrie to third base and playing Alex Cora at short. He also has Sean Casey available at first base, though Francona said he was hesitant about playing the veteran at first in this series because of the aggressive style of the Angels on offense.
Youkilis and Kotsay are more adept at handling the Angels' bunting game than the slow-footed Casey.
The Red Sox entered Monday leading the Angels, 2-1, in the best-of-five series.
Lowell went 0-for-8 in the series. After Lowell worked a walk in the 10th inning of Game 3, Francona felt he had no choice but to run for him.
"I just didn't think it was fair to put him in a position where if someone hits a ground ball in the hole and we're going to score a run, and he can't run to second and he's halfway there and they get an out they shouldn't, I can't let that happen," Francona said.
Lowell had been playing with pain in his right hip since late June, but it simply got to be too much.
"I think he's a little frustrated," Francona said. "Nobody questions his toughness. I mean, nobody. It's just getting difficult for him to be a baseball player right now. He can't move."
As recently as a couple of weeks ago, the injury would only bother Lowell on a certain kind of swing or an off-balance throw at third base. But it got far beyond that in recent days.
"I think it's affected him everywhere," Francona said. "Again, that's not a knock on him. When you do what we do for a living and you have a guy who is willing to try to [play], it's hard not to want to give him every opportunity possible. But he's hurting."