CINCINNATI (AP) - Tyler Chatwood felt pain in his triceps on a pitch in the third inning. Every time he threw his fastball, he felt it again.
The Colorado Rockies have another pitching concern.
Chatwood left after pitching four innings on Monday night, and the Rockies lost to the Cincinnati Reds 3-0. Bronson Arroyo limited the NL's most prolific offense to four singles in eight innings, and Jay Bruce had a two-run homer among his three hits.
The Rockies' pitching staff had a setback for the second day in a row. Chatwood left with a sore triceps after Rockies closer Rafael Betancourt went on the 15-day disabled list over the weekend with a strained groin.
"We wanted to leave him out there, but he was feeling it, especially on his fastball," manager Walt Weiss said. "It's the first time he's ever felt anything there."
Chatwood (3-1) batted in the fifth, bunted and was thrown out. Rob Scahill had been throwing in the bullpen and replaced Chatwood, who threw 64 pitches and allowed four hits and one run.
Colorado took him out as a precaution to get treatment. It's unclear whether it will force him to miss a start.
"They seem to think it's not serious, just a little inflammation," Chatwood said. "I've had soreness, but I've never had this kind of soreness. It was a little different."
The right-hander was coming off one of his noteworthy starts. He fanned a career-high 10 in six innings against Houston.
"It's frustrating to come out of the game like that when you're feeling good and leave your bullpen hanging like that," he said. "It was a precautionary thing and hopefully everything will be all right."
The Reds have three shutouts in their last four games. They've blanked six of their last 21 opponents, tying them with St. Louis and Pittsburgh for the league lead with nine shutouts this season.
Arroyo (6-5) allowed only one runner to reach second base while throwing 86 pitches that sometimes seemed oh-so-slow.
"I didn't have amazing stuff," Arroyo said. "Things just worked out. It was one of those games. I was able to keep guys off second base. Had some quick innings, kept my pitch count down. Some days the ball bounces your way."
Aroldis Chapman took the radar gun to a different level in the ninth, hitting 100 mph while fanning three and walking one. The left-hander got his 15th save in 17 chances.
Bruce scored on Todd Frazier's single in the fourth inning and hit his ninth homer off left-hander Josh Outman in the eighth.
Arroyo came in with a 4-8 career record against the Rockies, but kept them off balance from the start. The Rockies lead the NL in runs, but couldn't do much with Arroyo's unorthodox approach.
"He's tough, Arroyo," Weiss said. "He's good at reading swings and going back and forth and changing sequences and speeds."
The Reds have gone only 3-3 in the past week because of a slumping offense. They used a couple of well-placed hits to get a run in the fourth.
Bruce went the opposite way to left field, beating Colorado's infield shift, for a single with two outs. He stole his first base of the season and came around when Frazier flicked a low-and-away pitch to left field, one hand leaving the bat as he made contact. Bruce scored as Carlos Gonzalez's throw to the plate hit him in the back.
Zack Cozart singled in the eighth ahead of Bruce's homer, extending his hitting streak to a season-high eight games.
NOTES: RHP Juan Nicasio (4-2) makes his first career start against the Reds on Tuesday. Homer Bailey (3-4) starts for the Reds. ... Plate umpire Kerwin Danley took a deflected pitch off his facemask in the bottom of the first inning and needed a couple of minutes to recover. He left the game after the second inning, with Lance Barksdale moving from first base to behind the plate. Danley said he had a headache and would likely miss Tuesday's game. ... Reds 2B Brandon Phillips missed his second game after being hit by a pitch from Pittsburgh's Tony Watson on Saturday. Baker said Phillips' forearm is still very sore. Cesar Izturis started at second.
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