Wells gave up four runs, including a Brian Anderson solo shot, and nine hits in five innings of a 4-1 loss to the White Sox at Tucson Electric Park.
Wednesday could have been worse. Wells faced two runners on and one out in the first inning after a run had scored, and had the bases loaded and no outs in a third inning in which the White Sox scored twice. But he has improvement to make in consistency.
Any evaluation would have to include the hard-luck plays. Left fielder Seth Smith lost a leadoff fly ball in the sun in the bottom of the first, and it landed for a double. A potential double play didn't happen when the grounder tipped Wells' glove. But there was a simple theme to his highs and lows.
"I saw him get outs when he was down and give up hits when he was up," Rockies manager Clint Hurdle said.
With right-hander Jason Hirsh's sore right shoulder making it difficult for him to be ready for the start of the regular season, Wells is in competition with left-handers Franklin Morales and Mark Redman, and right-hander Josh Towers for the fourth and fifth rotation spots. Wells, signed to a $3.1 million contract during the offseason after going 7-17 with a 5.70 ERA in starting and relief roles with the Cardinals, could pitch out of the bullpen, also.
Wells had allowed 23 baserunners in 14 innings pitched, but Wednesday -- his longest outing -- marked the first time he didn't walk anyone.
"Actually, I was pleased in a sense that I threw strikes and eliminated the base on balls," Wells said. "I elevated a few pitches over the course of the outing."
It was a scoreless afternoon for a trio of Rockies relievers who threw one inning apiece. Ryan Speier gave up one hit, Taylor Buchholz threw a spotless inning and Ramon Ramirez struck out two and gave up one hit. Buchholz is pitching for a late-game role. Speier and Ramirez, each of whom have a 1.50 ERA, are battling for roster spots.
Second-base candidates also made their impressions. Jeff Baker turned a difficult double play off a dazzling flip from shortstop Troy Tulowitzki in the third inning, and Jayson Nix singled after coming off the bench.
Thomas Harding is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.