Brayan Bello will be activated from the injured list and make his season debut against the Seattle Mariners on Tuesday, manager Alex Cora announced Monday morning.

The right-hander will start against the incoming Seattle Mariners, who were also his opponent when he started Opening Day last year.

The Red Sox have been without Bello and fellow starter Lucas Giolito since before Opening Day. Right shoulder inflammation early in spring training put Bello behind the other starters. Giolito, who missed all of last season after needing UCL surgery during spring training, was supposed to be ready for Opening Day but suffered a mild hamstring strain on the first pitch of his Grapefruit League debut.

“We’ve been two guys down, but obviously he’s a big part of what we’re trying to accomplish,” Cora said of Bello. “Velocity is up, which is very important to us. The action on his pitches are good, and we know what he can do. … Hopefully we can get five out of him and move on to the bullpen, but I’m excited about him.”

This will be Bello’s second consecutive season debut against the Mariners, whom he faced on Opening Day in Seattle last year.

“I think he learned a lot throughout the season,” Cora assessed. “Didn’t start it well.”

Bello posted a 5.32 ERA over 17 starts in the first half, but improved immensely down the stretch, pitching to a 3.47 ERA over 13 starts in the second half. After getting hit to the tune of a .277 average and .796 OPS in the first half, he held opponents to .219 and a .629 OPS in the second.

“We reintroduced the four-seamer for lefties, I think that was very important,” Cora said. “And he learned how to use it, changed speeds, velocity was good throughout the season, and for him to go 30-plus starts, I think it was, right, that was very important, and now he understands.”

Cora’s advice to Bello?

“Just go out there and pitch, that’s the most important thing. Don’t try try to overdo it, especially in the first one. Just get your reps, see how it goes.”

After Bello, Sean Newcomb and Garrett Crochet are scheduled to start for Boston in the three-game series.

Giolito will either make one more rehab start or be activated.

“He felt great, threw strikes, physically he’s in a good spot,” Cora said of Giolito’s fourth rehab outing, with Double-A Portland on Sunday.