LOS ANGELES -- The Rockies have asked right-hander Aaron Cook, who hasn't pitched this season because of a broken right ring finger suffered during Spring Training, to make one more Minor League rehab start.
Cook, who could have come back after pitching Sunday at Triple-A Colorado Springs, will throw again for the Sky Sox on Thursday at Fresno. His return to the Rockies' rotation will be June 8 against the Padres at PETCO Park.
The decision also means righty Juan Nicasio, who gave up one unearned run in seven innings in a victory over the Cardinals on Saturday after being called up from Colorado Springs, will start Friday against the Giants at AT&T Park.
Rockies manager Jim Tracy said the extra start will allow Cook, 32, the Rockies' career leader in wins (69) and innings (1,215 1/3), to increase his stamina. Cook threw 99 pitches in 7 2/3 innings at Colorado Springs on Saturday and gave up eight hits and six earned runs. Relying on his sinker, he forced 13 ground-ball outs.
Colorado Springs pitching coach Doug Linton and organization pitching instructor Bo McLaughlin monitored the start for the Rockies.
"It's not so much how he is going to pitch, how many ground balls is he going to give up," Tracy said. "It's the stamina part of it -- building additional stamina and feeling like you've crossed every bridge before putting him back on the Major League mound."
Cook, who hadn't even faced hitters before suffering the injury during the spring and made three rehab starts at Double-A Tulsa before making the start for Colorado Springs, said he has been throwing four pitches effectively. Although the Rockies felt there was reason to delay his return, Cook said he is headed in the right direction.
Last year, Cook struggled to go 6-8 with a 5.08 ERA. His season was interrupted by a toe injury, which allowed him to go to the Minors to clear up mechanical issues. It was ended on Sept. 8 when a line drive by the Reds' Joey Votto cracked his left fibula.
"Bo McLaughlin, a guy I have a lot of respect for, said [Sunday] was the best he's seen me throw in two years," Cook said. "Balls were down. I was pitching to both sides of the plate effectively."
Outside of ace righty Ubaldo Jimenez (0-5, 5.86 ERA), who has battled injuries and inconsistency, the rotation has thrown well, but the loss of lefty No. 2 starter Jorge De La Rosa for the season because of a torn elbow ligament has hurt from an experience standpoint.
"I want to be here and I want to help out," Cook said. "I hope they've seen my commitment to this team. I want to be a part of something great. I think we have a great team here. We've struggled in May very badly, but we've got a great opportunity to do some wonderful things here."
The upshot of delaying Cook's return is Nicasio, who throws his fastball in the upper 90s and has a reputation for fearlessness, has a chance to show he's more than a stopgap. Another strong start could cause Tracy to juggle the rotation to make sure there's room for Nicasio.
"We want the best group of guys that we feel give us the best chance to win going forward, so he gets another opportunity as do other guys," Tracy said. "Aaron Cook is a veteran guy that has had quite a career here in Colorado. Rather than pin anything down, which is not necessary to do at this point in time, let him go out there and pitch. Depending on what we see in start No. 2 from Juan Nicasio, does it force you back to the drawing board and have you feel as though you have to realign some things because he's forcing himself in?"
Smith returns to Rox after mild groin strain
LOS ANGELES -- Rockies right fielder Seth Smith returned to the lineup Monday night against the Dodgers after missing three starts with a mild right groin strain.
Smith entered the game hitting .303 with five home runs and 22 RBIs and has been one of the Rockies' few consistent performers during a difficult May (.301, three homers, 10 RBIs in 23 games). Smith said he sees the team turning the corner. The Rockies beat the Cards, 15-4, on Saturday, and clawed back after early offensive woes but lost Sunday's game, 4-3.
"It seems like it's been awhile since we've battled back toward the end of the game, where we give a team a run for their money," said Smith, who struck out in a pinch-hit appearance Sunday. "That was good to see.
"It's not happening as fast as we wish it would, but it shows signs it's heading in the right direction."
Meanwhile, outfielder Ryan Spilborghs suffered a slight left groin strain while running the bases in Sunday's loss. Manager Jim Tracy said he was possible Spilborghs would be availabe to pinch-hit Monday, but he would need a pinch-runnner if he were to reach base.
Unselfish Herrera takes bump to bench in stride
LOS ANGELES -- Rockies infielder Jonathan Herrera prides himself on providing what the team needs.
For now, at least, that means giving up his starting spot at second base.
Recent callup Eric Young Jr. received his fourth start in the leadoff position on Monday night. Young, who was 5-for-14 in the previous three games, has made his last three starts at second base. Young and center fielder Dexter Fowler, who has dropped from leadoff to Herrera's former No. 2 spot, provide top-of-the-order speed.
That means Herrera has returned to his former job description of utility man.
"You just have to be ready when those things happen, when you're not in the lineup," said the switch-hitting Herrera, who is hitting .271 after hitting .300 in April. "For me, I don't really worry about me. I worry about the team.
"Everything they've been doing with our lineup is just trying to win. All 25 guys have to do something to help the team win. I'm getting ready every day, looking for something to help the team win."
Rockies manager Jim Tracy said he discussed the situation with Herrera and Young and said there would be playing time for both. Herrera could replace Young late in games for defensive purposes.
"Both players are on board," Tracy said. "Both players understand exactly what it is. We're going to use our resources, each and every one that gives us an opportunity to win the game."
Thomas Harding is a reporter for MLB.com. Read his blog, Hardball in the Rockies, and follow him on Twitter @harding_at_mlb. This story was not subject to the approval of Major League Baseball or its clubs.