But Chacin was more than just alright Wednesday night, taking a no-hitter through 6 2/3 innings, the longest bid by a Rockies pitcher at Coors Field in franchise history. (The next closest was John Thomson, who threw 6 1/3 hitless innings on May 2, 2002). Though the bullpen had to weather a Giants rally in the eighth, Chacin's brilliant start was enough for a 5-4 win.
"This morning, when I woke up, I called them and said I feel better," said Chacin, his voice strained form the lingering effects of the sickness. "I always want to pitch, so it has to be really bad."
The win handed the Rockies their second straight series victory, improving to 3-1 on the homestand before Thursday's day off. They start a three-game set against the Reds Friday.
Chacin feasted on the Giants' lineup with a fastball firmly planted in the strike zone, a curveball that left players wagging their bats and a slider he turned to for groundballs.
Giants shortstop Brandon Crawford ended Chacin's no-hit bid with a two-out single into shallow center in the seventh inning. Charlie Blackmon did his best to chase down the ball, but was positioned much too deep in the outfield, the crowd of 27,268 letting out a hearty cheer in recognition of Chacin's terrific outing once it dropped.
"It was not high enough for what I wanted, and the ball may have run back a little," Chacin said. "But it was the pitch I wanted. It wasn't like I hung it or something."
Chacin admitted he couldn't entirely push aside the thought that he was dancing with history, inching closer to tossing the second no-hitter in Rockies history with each out.
"How can't you be aware?" said Chacin, "Just don't try too hard or anything like that. Just keep making my pitches, keep throwing the pitches low in the zone and make them swing."
The right-hander struck out nine -- three short of his career high -- with two walks and an unearned run the only blemishes on his resume. And Weiss had no plans to stand between his pitcher and the once-in-a-career moment, despite a pitch count that climbed to 108 after seven innings.
"If there's no hits, he's staying in," Weiss said. "I'll let him go."
Of the six Giants that reached base on Chacin's watch, three were on errors. Those miscues drove up his pitch count and allowed the Giants to take a 1-1 game into the bottom of the sixth.
Wilin Rosario, who made two errors at first base, redeemed himself in the sixth with a bloop single to center that scored DJ LeMahieu and pushed the Rockies ahead, 2-1. Catcher Yorvit Torrealba sent a ground-rule double over the right-center-field wall with the bases loaded to score two more, and Chacin himself plated Nolan Arenado when he beat out the throw at first on an attempted inning-ending double play.
The Rockies' four-run rally chased Giants starter Madison Bumgarner (11-9), who allowed four runs in 5 1/3 innings, striking out six.
LeMahieu kept Chacin's no-hitter alive and saved a run in the third when he made a diving stop just beyond the infield dirt with runners on first and second after back-to-back errors by Rosario at first base. LeMahieu spun around and made the throw to first from his knees just in time to rob Marco Scutaro of a potential RBI single.
"What makes him so good is he doesn't leave you anything really in the middle of the zone," Giants first baseman Brandon Belt said. "He kind of nibbles around a little bit and he makes you go after his pitch."
The Rockies struck first when Arenado doubled into deep left-center to plate Rosario, who led off the second with a single to center.
San Francisco evened the score in the fourth thanks to a rare error by shortstop Troy Tulowitzki. Belt led off the inning with a walk before Buster Posey smacked a grounder toward Tulowitzki, the ball bouncing off his glove and into the outfield to move Belt to third.
Only adding to the intrigue was that he escaped jams in the third and fourth that were not of his own creation but the product of a string of defensive errors.
"Pounded the strike zone with the fastball, offspeed was unreal," Torrealba said. "He was able to make his pitch whenever he needed to, especially after getting a couple errors."
That allowed Belt to score when Hunter Pence hit into a double play.
Reliever Wilton Lopez took over for Chacin in the eighth and allowed two runs. Lefty Josh Outman took over and fared no better, allowing the Giants to cut Colorado's lead to 1, before Matt Belisle finally finished off the inning.
Rex Brothers sealed the series victory with a perfect ninth inning, striking out two to pick up his 14th save.
It was yet another example of how pitching has, at times, carried the Rockies -- a puzzling thought for a club that plays half its games at a notoriously hitter-friendly park.
"Our pitchers have really stepped up this year, particularly our starters," Weiss said. "Our guys take pride in the fact that they've got to be tougher to pitch here, and that's what they've done. They don't ever talk about where they pitch."