When Boston Red Sox third baseman Alex Bregman went down with an injury on Friday, Boston fans left the stadium wondering how serious the star third baseman's injury actually was.The severity of the injury has been revealed and, according to Red Sox manager Alex Cora, Bregman will be out for an extended period of time.According to Jen McCaffrey of The Athletic, Cora called Bregman's injury "significant" and said it was very similar to his 2021 quad strain that caused him to miss more than 50 games.The removal of Bregman from the Boston lineup will be a major loss. He was hitting .299 with 17 doubles, 11 home runs and 35 RBIs in 197 at-bats. He was well on pace to top his numbers from last season, and his bat will be hard to replace over the next two-plus months.Bregman spoke on his injury and explained how he'd been feeling since being removed from Friday's game."I felt better (Friday) when I got hurt. Then last night I couldn't really fall asleep, so I started to hurt pretty good," he explained, per NESN.com. "Then, after the MRI, I found out it was pretty severely strained, and now it's time to focus on rehab. Neither of (the injuries) really felt that good."While they wait on Bregman to return, the Red Sox will hope to get production from their No. 2 prospect Marcelo Mayer. He is a career .273 hitter with 46 home runs and 48 stolen bases in over 1,200 minor league at-bats.Mayer was promoted to the major leagues Saturday, prior to Game 2 of Boston's doubleheader against the Baltimore Orioles. The debut didn't go quite the way most had hoped, as he was 0-for-4 with three strikeouts.Despite the underwhelming performance in his debut, the future for Mayer is bright. Alongside young star Kristian Campbell, Mayer will have a chance to play every day and prove himself as a major league caliber player.More MLB: Former Phillies, Mets, Red Sox Pitcher Announces Retirement