The Red Sox have been leaning on their bullpen hard all week long, and Sunday the club brought in another fresh arm to help get them to the end of the homestand.

Prior to first pitch the club announced that right-hander Zack Kelly has been called up to the big league club and that fellow right-hander Luis Guerrero has been optioned to Triple-A. Guerrero had just come up on Saturday and pitched in the second game of the day’s doubleheader, but with the Red Sox in need of arms he went right back down following the game.

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Kelly has appeared in seven MLB games this season, allowing 10 earned runs in 10 innings. The 30-year-old has struggled in Triple-A as well, posting a 9.28 ERA with 14 walks in 10.2 innings, but Red Sox manager Alex Cora noted that he boasts great stuff and the problem for him as always been consistency.

“He’s been ok, I think where we’re at we need to keep making moves to reset the bullpen, it’s been hard the whole week, it started against Atlanta and it hasn’t stopped,” Cora said. “So having a fresh arm will help us.”

Guerrero allowed one earned run in 1.1 innings in Saturday night’s 2-1 loss, which was the first earned run he’s allowed in 13 career MLB appearances dating back to last September.