Considering Thornburg hadn't pitched in any kind of regular season game -- Minors or Majors -- since 2016, it was an impressive opening.
Thornburg will pitch again for Pawtucket on Wednesday and continue a gradual progression from there.
"It was good. Especially since it hadn't exactly happened in a while," Thornburg said. "It was a cold and rainy night and I'm used to pitching in 80-degree weather. About as good as I could've hoped, honestly. So not bad at all. I guess we'll see what happens in the second and third [outings] and so forth."
Thornburg had surgery to repair thoracic outlet syndrome in his right shoulder in May 2017.
He could become a key component in Boston's bullpen when he returns.
"He's another different look, 95 with the breaking ball and a changeup," manager Alex Cora said. "That's another guy that we can match up with whatever we feel we're comfortable. We're trying to patch up 27 outs, and he's going to be a part of it."
"That's hard to predict," Cora said. "With him, we know how hard the road has been, and I don't want to put a timetable. For me, go tomorrow, do your thing, and we'll go from there. We'll go on a daily basis, but he has to go through a few steps. Back-to-back days. Traffic. Coming in in the middle of an inning. But his first step, it was a big one, and it was great. That was fun to watch."
Mookie to return Wednesday Right fielder Mookie Betts, who missed the past two games with tightness in his right hamstring, was healthy enough to start on Tuesday. But with a day game looming on Wednesday, Cora decided to hold him out one more day, though Betts was available to pinch-hit.
"With Mookie, he wasn't going to play back-to-back days -- you know, day game after night game -- so I decided, for us, it's better for him to start tomorrow," Cora said before Tuesday's game. "There's a lefty on the mound, so I didn't want too many lefties in the lineup. He's ready to play. It's just a matter of which one he was going to play, and I just decided to play him tomorrow."
Pedroia re-starting laser show Dustin Pedroia had another productive day at extended spring training, at least judging by the text the second baseman sent to his manager.
"Pedroia, and I quote, 'Three innings, four great plays at second base, 1-for-2 with a laser.' He played today so he feels good," Cora said.
Kelly returns Wednesday The Red Sox will get a key piece of their bullpen back on Wednesday, when Joe Kelly's six-game suspension ends.
"Yes, he threw yesterday -- an up and down, one of those bullpens, and he's ready to roll," Cora said.