There may have been two All-Star pitchers scheduled to start Friday night's game at Great American Ball Park, but only one looked the part.

Edinson Volquez picked up his fourth loss of the season in Friday's 7-2 loss to the Rockies, lasting just four innings and leaving his team trailing 5-1, while Rockies starter Aaron Cook improved to 13-6, allowing a run on five hits in eight innings of work.

"Like I said to (pitching coach) Dick (Pole), he said not to worry about it, but I have to worry about it, because I don't want pitch like that again," Volquez said.

Since dominating the Yankees at Yankee Stadium on June 20 to improve to 10-2, Volquez has gone 2-2 with a 5.97 ERA, allowed 39 hits, 24 runs, 16 walks and stuck out 24.

"I think I'm doing something different in my mechanics right now, I don't know what it is, but I've got to look at my mechanics and see what's happening," Volquez said. "I'm missing a lot in the strike zone, I'm missing my spots and I've got to work on it."

The Rockies scored two on Volquez in the first on a walk and two hits and three more in the third on a solo homer by Jeff Baker and a two-run homer from Brad Hawpe.

Volquez labored throughout his start, throwing 28 pitches in the fourth inning despite not giving up a run. In all, he threw 99 pitches, 59 strikes.

"If you ask him, he'll tell you he's not fatigued, and his velocity will show you that," Reds manager Dusty Baker said. "But also (the opposition) making adjustments, guys look at video rooms to pick up things. Now it's up to him and us to make that adjustment. Nobody goes through a whole season without getting hit a little bit. What he was doing before was unbelievable and I think get back to that sometime again. He needs to get through this and we need to help him. We need to keep his confidence up and his focus and concentration."

Cook threw six fewer pitches than Volquez in twice the innings and was helped by several good defensive plays, including one of his own to retire Ken Griffey Jr. in the eighth inning.

The Reds scored one run on an Edwin Encarnacion's broken-bat single in the second and tacked on a run with two outs in the ninth on Paul Bako's double.