The devastating news broke over the weekend ... Bieber -- who was untouchable in his first two starts this season -- will sit out the rest of the 2024 campaign after it was revealed he'd undergo Tommy John surgery to fix damage to his elbow.

Tony Clark of the MLB Players Association singled out the league's recent pitch clock adjustments as the reason behind the uptick in pitcher injuries recently ... but the MLB fired back, citing research that found no evidence that tied injuries to the new tweaks.

Bieber was asked about the narrative behind the trend ... and while he acknowledged the chatter, he isn't ready to pick a side.

"Obviously, the conversations are happening," Bieber said. "They're continuing to grow louder and they're happening quite a bit more often. So, we'll see what's to come of it."

"For me, I'm not ready to say what it is. I guarantee it's a combination of a number of factors. And also, all of that on top of logging a lot of innings from now all the way back into college and high school."

Bieber added he started to feel irritation in his arm during the middle innings of his outing against the Oakland A's ... but admitted he thought it was due to Opening Day soreness and the cold temps.

The ace was emotional as he spoke with reporters ... saying it's especially tough, as he just fell back in love with pitching again after hitting a rough patch in his career.

Regardless, Bieber said he will be there for his guys every step of the way ... just in a different capacity.