The Rockies designated Lopez for assignment on June 16. But with three starters (Brett Anderson, Tyler Chatwood and Eddie Butler) disabled, and with callups Christian Bergman, Tyler Matzek and Christian Friedrich in the rotation, the bullpen needed protection. Lopez, 0-2 with a 4.54 ERA in Colorado Springs, suddenly found himself needed.
Long relievers Tommy Kahnle and Franklin Morales have been used heavily.
"A lot of it has to do with where we're at right now as a pitching staff," Rockies manager Walt Weiss said. "Our bullpen has been pretty taxed and I feel like we needed another guy that can give us multiple innings out there. That's one of the major reasons we brought 'Lopie' back. He's been throwing the ball better."
Lopez had some strong performances for the Astros from 2009-12, with many of those coming as a closer, but he lost the sink on his sinker when he arrived with the Rockies and the results have been predictable -- 3-4, 4.63 ERA, 106 hits against in 81 2/3 innings over 79 total appearances with Colorado.
Lopez believes he has found something.
"I worked every day -- I threw hard, and I focused on location, inside and outside, and threw my slider," Lopez said. "I wanted to get more power in my arm."
To make room for Lopez on the active roster, the Rockies optioned righty Chris Martin (0-0, 6.89 ERA) to Colorado Springs. The club also placed outfielder/first baseman Michael Cuddyer (fracture in left shoulder socket) on the 60-day disabled list to open a 40-man roster spot for Lopez.
The Rockies also recalled Friedrich from Colorado Springs for Saturday's start, his 2014 debut, and optioned first baseman/outfielder Kyle Parker to Colorado Springs. Parker, the team's No. 1 Draft pick in 2010, went 0-for-6 with four strikeouts -- three in his only start, when the Dodgers' Clayton Kershaw no-hit the Rockies at Dodger Stadium on Wednesday night.
Thomas Harding is a reporter for MLB.com. Read his blog, Hardball in the Rockies, and follow him on Twitter @harding_at_mlb. This story was not subject to the approval of Major League Baseball or its clubs.