BOSTON -- Red Sox slugger Triston Casas provided details Friday on his left rib cage injury that will keep him sidelined for a minimum of a few weeks.

The first baseman revealed he has torn cartilage. There was no break in the bones of his rib cage.

¡°No ribs were fractured,¡± Casas said. ¡°It's not a bone thing. It's more a cartilage thing. So there's the ribcage and then there's the sternum, and there¡¯s pieces of cartilage that are in between those that connect the two. And that was what was torn, was the cartilage.

¡°The way that the doctors kind of explained it to me is that one isn't better than the other. [Whether the injury] was a muscle or a bone or cartilage, they¡¯re all similarly timetabled schedules. Everything in the midsection just takes a long time to heal and mend, and there's a lot of torque and rotation that happens during the swing, so everything needs to be perfect.¡±

In other words, the cartilage needs to heal fully before Casas can ramp back up for a return to action.

Was the 24-year-old given any kind of timetable from the doctors for how long the healing process might take?

¡°They said anywhere from three weeks to six weeks to nine weeks, ¡° Casas said. ¡°They don¡¯t know. It¡¯s just depending on how my body is feeling. But for right now, I'm still in pain to breathe. My lungs are still hitting my midsection which I¡¯m still getting to like 75 percent capacity without pain.¡±

Even without a precise timetable, Casas expressed confidence that he will be back in the lineup for a significant portion of the 2024 season.

¡°Very optimistic,¡± Casas said. ¡°I'm feeling better right now with movement every single day. I haven't really thought about the progress I've made in these last couple days. So I'm happy about where I'm at compared to where I was feeling five days ago. So hopefully, I keep getting better every day. That's the plan, and I can hit the ground running right when I get off the IL. So yeah, I anticipate playing for a good amount of the season.¡±

Casas knows there are no shortcuts he can take in the process of returning to the active roster.

¡°The first step is to feel good breathing before I can move to cardio and then move into more anaerobic exercises and then progress as I go there,¡± Casas said. ¡°But that's the first step to feeling better is just breathing without pain. So that's what I'm working on now.¡±

Casas came out of Boston¡¯s game at Pittsburgh on April 20 after fouling off a 3-1 pitch left him wincing in pain. The injury had started to form in his first at-bat against Ben Lively in a game against the Guardians three days earlier, but the left-handed hitter didn¡¯t realize at the time how significant it would be.

¡°After that, I was trying to manage it with the trainers, but it was a couple of days, and my body gave in [on April 20],¡± Casas said.

The doctors indicated to Casas that the injury wasn¡¯t from a specific movement, but likely from years of swinging the bat ferociously with his 6-foot-5 frame.

¡°From what the doctor explained to me, he said that he had seen these types of injuries in football players and hockey players,¡± Casas said. ¡°And he had asked me if I had had a collision in the past of some sort that would merit some pain in my midsection. And I told him, ¡®No.¡¯

¡°And he pretty much chalked it up to me being so big, rotating so fast so many times that I pretty much created a car crash within my body. And it was a matter of time before this happened. He said it was something similar to a pitcher needing Tommy John, just an inevitable thing that was going to happen sooner or later.¡±

As for Casas, a key cog in Boston¡¯s lineup, he just hopes his return is sooner rather than later.