Rivera, who turns 25 on April 13, in 2005 became the first pitcher to throw a perfect game in the Mexican Summer League playoffs, and went 9-7 with a 3.73 ERA in 2006. Currently, he is 5-2 with a 2.32 ERA in nine starts for Mayos de Navajoa in the Mexican Winter League.
The Rockies can bring back all five rotation members from 2006, but they're seeking rotation depth even if they don't trade No. 1 starter Jason Jennings, whose name has cropped up in many reports of possible trades. Rivera provides an alternative option to trades and Major League free agency.
Former Rockies standout Vinny Castilla recommended Rivera, who has been impressive in Winter League games against Rockies outfielders Choo Freeman and Ryan Spilborghs. Rockies scout Mike Paul said that Rivera has enough ability to help the team.
"I would classify him as a crafty left-hander," Paul said. "He's not overpowering, but he's got a good feel for pitching. He has a great changeup. He can throw it to left-handers, right-handers, he doesn't care. It's a good pitch for him.
"He uses both sides of the plate with his fastball. He's not afraid to pitch inside. In fact, I was just down there, and took Freeman and Spilborghs out to dinner. I was talking to Choo about him and said, 'Choo, remember the left-hander named Rivera?' He said, 'That's the guy that ran that fastball in on me.' "
Bill Geivett, Rockies assistant general manager, said that several other clubs have pursued Rivera, but the Yucatan club resisted. However, Colorado has built a good relationship with the Leones, and Rivera wanted the shot with the Rockies.
Rivera told the Web site purobeisbol.com that he is confident that he can impress the Rockies.
"I'm going to work hard in order to take advantage of this opportunity with the Rockies. I feel real happy with this opportunity," Rivera said. "I have seen a lot of great pitchers with great velocity, but in my opinion, my control and my changeup, curve and slider have given me the best results."