"I'm surprised he threw four balls," joked right-hander Brandon Workman.
Uehara struck out two of the three batters he faced in Boston's 7-6 loss.
"He continues on, that's the best you can say," said Red Sox manager John Farrell. "And after four or five months down, he picks up where he left off, and he's just a joy to watch pitch."
Originally, Farrell was going to hold Uehara and setup man Junichi Tazawa back until later in the spring because of their workload during the postseason.
But both Japanese righties made their debuts on Monday. Tazawa worked around one hit in his scoreless inning.
Why the change in schedule?
"Sitting down with both of those guys and looking at the schedule, we're playing some National League teams, and they're going to have ample rest in between their outings," Farrell said. "We still target roughly seven outings in Spring Training for both of them. We can use the schedule somewhat to our advantage."