Walker Buehler flew back to Boston on Wednesday in anticipation of his scheduled start against the Minnesota Twins at Fenway Park on Friday.

Instead, the veteran right-hander is undergoing testing on his shoulder, and regardless of whether he needs an injured-list stint, won’t take the mound on Friday.

“We’re working through a few things regarding Walker,” manager Alex Cora told reporters on Thursday afternoon, before the series finale with the Blue Jays in Toronto. “He hasn’t bounced back the way we wanted, so we have to wait.”

Brayan Bello will take the mound Friday, instead. Garrett Crochet will close out the series on Sunday, but Red Sox haven’t announced a starter for Saturday.

Buehler, a two-time All-Star and World Series champion with the Los Angeles Dodgers, signed a one-year, $21.05 million contract (with a mutual option for ’26) during the offseason. Through six starts totaling 33.2 innings this season, he owns a 4.28 ERA and 1.218 WHIP. Since allowing a combined nine earned runs in his first two starts, however, Buehler has posted a 2.59 ERA and allowed just seven earned runs in his subsequent four outings.

Rookie Kristian Campbell was also a late scratch from Thursday’s lineup due to right rib discomfort. Campbell has spent the bulk of his rookie campaign at second base, but was due to start in center. Instead, Rob Refsnyder will start in left while Jarren Duran moves to center.