Red Sox pitcher Brayan Bello is set to make his spring training debut on Sunday against Atlanta. Gerald Herbert/Associated Press

The Red Sox open Grapefruit League play this weekend – and their major league starters are getting thrown into the fire immediately.

After non-roster invitee Helcris Olivarez started in the annual exhibition opener against Northeastern on Friday, Boston will begin rolling out its big league rotation candidates against major league opponents starting Saturday. Manager Alex Cora said righty Garrett Whitlock will pitch Saturday against the Orioles in Sarasota, Florida. Righties Brayan Bello and newcomer Lucas Giolito will start Sunday. Bello is expected to pitch against Atlanta in North Port, Florida, and Giolito will face the Twins at JetBlue Park in Fort Myers.

Nick Pivetta will pitch Monday at home against the Phillies, with righty Kutter Crawford and lefty Brandon Walter each pitching Tuesday against the Cardinals in Jupiter. Josh Winckowski will get the ball Wednesday in West Palm Beach against Washington.

Bello, Giolito, Pivetta and Crawford are locked into rotation spots, but there’s an open competition for the fifth spot. Whitlock, Tanner Houck and Winckowski are the top three candidates to make the starting five, with Walter a long shot the Red Sox are stretching out to serve as Triple-A depth in Worcester.

The Red Sox have not yet named a starter for Opening Day, which is March 28 in Seattle.

GIOLITO SPENT the majority of his big-league career with the Chicago White Sox, so he was used to how his former team did things. In his first spring training with the Red Sox, Giolito has high praise for their focus on development.

“I’d say that the program here, it’s all about development,” the right-hander told Chris Cotillo and Sean McAdam on MassLive’s “Fenway Rundown” podcast. “Things that were just said today in our meeting, like the development doesn’t stop at Triple-A. We get to the big leagues, we still have a huge team. You want to get a pitch better, you feel something mechanically off – go and talk to these guys.

“I’d say that the program here, it’s all about development,” the right-hander told Chris Cotillo and Sean McAdam on MassLive’s “Fenway Rundown” podcast. “Things that were just said today in our meeting, like the development doesn’t stop at Triple-A. We get to the big leagues, we still have a huge team. You want to get a pitch better, you feel something mechanically off – go and talk to these guys.

“But at the same time, there’s respect for kind of how everyone works, which I appreciate. The communication level is extremely high. If you want to go in and look at all the skeletons and biomechanics and study analytics, there are guides for that. If you prefer not to, then maybe it’s communicated to (pitching coach Andrew) Bailey and then he comes to us with whatever suggestion. So it really can be catered to every individual player because we’re all unique and different.”

The Red Sox rotation a mix of veterans, newcomers and pitchers who have been in big leagues but are fighting for the final spot in the rotation. So they all have different needs, areas where they need to improve and areas where they strive. Having someone like Bailey, who used to pitch for the Red Sox, is also helpful when it comes to helping get the most out of those on the mound.

Being able to go into spring training knowing what you want to work on and knowing you’ll have the support to continue to develop yourself will certainly be beneficial to not just Giolito, but pitchers like Bello, who’s expected to take a big step this season, and Houck, who like Whitlock, has been in and out of the rotation.

RED SOX 7, NORTHEASTERN 2: Mark Contreras hit a three-run home run in the third inning and the Red Sox beat the Huskies in a seven-inning game at JetBlue Park in Fort Myers, Florida.

Nathan Hickey, who played 80 games for the Portland Sea Dogs last season, had an RBI double in the second and Phillip Sikes added an RBI single for the Red Sox, who fielded a lineup of primarily minor leaguers.