So impressively, in fact, that manager Terry Francona told WEEI's Dale and Holley Show that the 23-year-old is "penciled in" to start this weekend in Texas.
Tazawa, who lasted 1 2/3 innings before surrendering a walk-off home run to Alex Rodriguez in his major league debut on Friday, showed he was capable of handling himself on the Fenway mound.
He induced a sure double-play ball, but Nick Green's feed to Dustin Pedroia was off the mark, and the Red Sox failed to record an out. Tazawa again induced a double-play ball, but the transfer was too slow. Both plays resulted in runs scoring, and Tazawa left the mound after the first trailing 3-0.
After that, however, Tazawa looked strong. He recorded six strikeouts, including a pair of punchouts to end the third inning with a runner on third.
"I thought he showed exceptional poise," Francona said after the game. "Then, as he got into the game, he started getting comfortable, he started locating … I thought that was an exceptional performance.