"It was the best day so far," Buchholz said. "Probably threw close to 50 pitches, up and down three times. Like I said, the best I've felt, as far as intensity and everything."
Buchholz will repeat the exercise on Saturday at Fenway Park. Assuming everything stays on track, he will face hitters after that, most likely in a simulated situation before going on a Minor League rehab assignment.
The Red Sox still expect Buchholz to have time to pitch multiple times in rehab games before the Minor League season ends in early September.
Buchholz is past the point of targeting a return date to the active roster.
"I've already tried that and it didn't work out too well. I'll just let it happen when it happens," Buchholz said.
Ian Browne is a reporter for MLB.com. Read his blog, Brownie Points, and follow him on Twitter @IanMBrowne. This story was not subject to the approval of Major League Baseball or its clubs.