Entrusted with a 4-3 lead entering the bottom of the ninth, Tazawa gave up two singles and a wild pitch, setting up a game-tying sacrifice fly by Adeiny Hechavarria. The Red Sox lost, 5-4, in 10 innings.
"We believe in Junichi," said bench coach Torey Lovullo. "We know that he's capable of going out there and getting the job done. He didn't get the job done tonight. You can look in the past, look as far back as you want, and I'm sure there's a track record that can be had. But he's a competitor. He's going to go out there and get us three outs any time."
Tazawa, Jean Machi and Ryan Cook are three righties Farrell has mentioned as possibilities in the ninth inning.
Cook, Boston's lone acquisition at the July 31 non-waiver Trade Deadline, was recalled from Triple-A Pawtucket to take Uehara's spot on the roster. He worked around a hit and pitched a scoreless inning on Tuesday.
"We traded for Ryan. This is an opportunity to go take a look at another arm that has had some late arm experience in the past and has been successful," said Farrell. "We'll take a look at him in that similar role."
Lefty Tommy Layne also was summoned from Pawtucket to take the roster spot of Justin Masterson, who was designated for assignment following Sunday's game. He walked the only two batters he faced in the seventh, with one of them coming around to score.
The injury to Uehara was obviously unfortunate, but would have hurt more if the Red Sox were in contention.
"Everything points to him being full go in Spring Training," said Farrell.