Eovaldi appears to be some sort of freak.
Most pitchers who throw 100mph are freakishly tall, like Randy Johnson or Aroldis Chapman or Mat Latos. Eovaldi isn’t. Most starters dial it back and pace themselves. If you watched the All Star game, you probably saw a pitcher or two you normally see throwing 92-93 mph suddenly hitting 98mph routinely. I don’t think Eovaldi dials it back at all. He hits 99mph regularly, but I don’t think he could hit 104-105mph in a short outing. That’s approaching record-breaking velocity for a RHP. But that type of stamina that allows him to throw 98-99 that often is freakish (and probably why he gets injured a lot).
In closer role, Eovaldi would probably be looking at 30 one inning appearances the remainder of the season. Counting warmups, that’s probably about 40 pitches per appearance. However, the Sox could limit him further by not using him in 3 run save opportunities, which are fairly low risk. Most pitchers can get 3 outs before giving up 3 runs most of the time. So, say that means 20 save chances. At my estimated pitch count, that means about 800 pitches this year.
In the rotation, he would have 14 starts left. At 100 pitches per start, that’s clearly more pitches (1400, obviously). He’d get longer (and more consistent) breaks between outings, but throw a lot more. And as I said, I think he always goes full tilt.
I don’t think closing will be easy on his arm by any means. But I do think it will be better off...