However, they have not solidified the timing of the rehab assignment for rookie right-handed starter Jason Hirsh, who is recovering from a right ankle sprain.
Fuentes will pitch for the Tourists, who will play against the Class A Rome Braves on Tuesday. Fuentes was placed on the 15-day disabled list coming out of the All-Star break, but he's eligible to come back for Thursday's road game against the Nationals because he last pitched in a game on July 3.
Fuentes, 20-for-26 in save opportunities, missed the All-Star Game -- it was the third straight time he has been selected -- because of the injury.
Hirsh suffered his ankle injury while running the bases during his last start, a 6-2 victory over the Mets on July 2 at Coors Field. Hirsh held the Mets to three hits during six scoreless innings.
Last week, Hirsh was hoping to pitch an injury rehab start quickly, but manager Clint Hurdle said the nature of the injury forced the Rockies to be conservative.
"You've got to remember the injury is to his right ankle, which is his push-off ankle, which supports all his weight and his drive in unloading a pitch," Hurdle said. "That's not something you can entertain going any further unless he's 100 percent. I don't think it's far away, but it's not tomorrow."
Hurdle said Hirsh will have to be able to complete a bullpen session before pitching in a Minor League game.
Center fielder Willy Taveras, recovering from a strained right quadriceps, ran before Sunday's game and could be in the lineup on Monday when the Rockies begin a three-game set against the Pirates at PNC Park. Taveras needs to be comfortable beating out infield bouncers and stealing bases before he returns to the lineup.
Old story: The Rockies' 2-1 loss to the Brewers on Friday night was their eighth final at-bat loss this season, three more than all of last season. Half of the Rockies' last 10 road losses have occurred in such situations.
Unrewarded gem: Rodrigo Lopez's seven innings of one-hit ball on Saturday marked the fifth time in history that a Rockies starter has gone that far while giving up just one hit.
Lopez received a no-decision. Scott Elarton pitched seven one-hit innings on Sept. 22, 2001, but he gave up two runs and took a 3-1 loss in Montreal. Jason Jennings on Aug. 1, 2002, against the Pirates, Denny Stark on Sept. 24, 2002, against the Dodgers and Jennings on June 20, 2006, against the Athletics all won games that ended as shutouts. Only Jennings' game against the A's was at Coors Field.
Up next: Right-hander Taylor Buchholz (4-3, 4.65 ERA), who replaces Hirsh in the rotation, makes his first start since June 1 on Monday at 5:05 p.m. MT against John Van Benschoten (0-3, 5.40) and the Pirates.
Thomas Harding is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.