Rodrigo Lopez creates the uncertainty. Lopez will get an MRI exam on his forearm Monday. Lopez left Thursday's game with tightness in his right forearm, but he said he hoped to start Thursday against the Marlins. Manager Clint Hurdle was less optimistic.

That's where Hirsh comes in. Hirsh will join Colorado on its six-game road trip this week. He threw his third and final rehab start for Triple-A Colorado Springs on Saturday night, tossing 6 1/3 scoreless innings.

"Stuff felt good for the most part," said Hirsh, who said his ankle is no longer a concern. "My timing was off just a little bit. Physically, I felt great. My arm felt good. I threw predominately fastball-slider, maybe a handful of changeups."

Hirsh's reliance on his fastball was music to the ears of his manager. Hurdle has been pleading with Hirsh to throw more fastballs.

"For me, I think I have more confidence in his fastball than he does," Hurdle said. "And that's the point I'm trying to make to him. He's got a good fastball. He's got a much better fastball than he gives himself credit for."

Hirsh had shown progress the night he sprained his right ankle. He injured the ankle July 2 against the Mets while trying to get back to third base on a pickoff attempt by Mets catcher Paul Lo Duca.

"I'll definitely make sure that the next time I get on third base, I'm going to be sitting on it until the guy hits the ball," Hirsh said.

Hirsh had pitched one of the best games of his rookie season. He held the Mets scoreless for six efficient innings, throwing only 61 pitches.

Helton slumping: Hurdle said Sunday that he does not plan to move a slumping Todd Helton from the cleanup spot.

"You've got to consider everything that's involved with changing the order," Hurdle said. "You've got guys that are having some success. Brad Hawpe's having his best season hitting six. You want to go ahead and hit him fourth in a pennant race for the first time in his career? That's your option.

"And I haven't made that move yet, and it's not on my to-do list. Not that he's not capable, but I think the timing is critical. And I like what we're getting out of Brad at six. Todd is giving us what he's giving us at four."

Helton's hitting struggles started in the middle of May. Before May 12, he was hitting .397; he's hit .249 since. In his last eight games entering Sunday, he's 2-for-19. However, Helton is still feared in the Rockies' lineup. He ranks third in the National League with a .423 on-base percentage, and he ranks second in the NL with 79 walks.

Matsui to sit out next two: Jamey Carroll got the start Sunday at second base. Because of Kaz Matsui's struggles, and with Marlins left-hander Scott Olsen starting Tuesday's series opener in Florida, Carroll will start Tuesday, as well.

Matsui has just three hits in his last 29 at-bats, and he is 6-for-48 since the All-Star break. Matsui said he hasn't been pitched differently, but his struggles are mechanical.

"It's when my body goes forward," he said. "That's the thing I have to correct."

Hurdle had a similar assessment.

"He's shown the ability to hit the ball hard the other way," Hurdle said. "That's been a little nonexistent so far.

"He's not covering the ball away and spinning off the ball in. You never like that, but those are things you have to deal with. He's a pro. He'll find his way back."

Buchholz staying in the 'pen: Don't expect Taylor Buchholz to get another start this season. Buchholz has filled in as starter because of injuries in the Rockies' rotation this year, but he has a 1.20 ERA this season since moving to the bullpen in June.

"We just feel at this point in time Buchholz is much more comfortable in the bullpen," Hurdle said. "When we've asked him to make some adjustments, there's so much effort there that it's been counterproductive."

Up next: The Rockies are off on Monday and then travel to Florida for a three-game series. Aaron Cook (7-6, 4.22 ERA) will start Tuesday's 5:05 p.m. MT opener against Olsen (8-8, 5.31).