Speaking conservatively, Rizzo said he believes that both players can be the in big leagues by late 2007 or by the beginning of '08.
"They are both very good prospects. Of course, we gave up an established Major League pitcher in Livan," Rizzo said on Monday night. "That I know them, drafted them and signed them is a comfort to me because I know what kind of people that they are, what kind of players they are. I have a real good feel for it."
Rizzo said he is not concerned that Mock was 4-8 with a 4.95 ERA for Double-A Tennessee entering Monday's action. He pointed out that Diamondbacks right-hander Brandon Webb had a similar year when he was close to being big-league ready in 2001. Webb went on to become an All-Star pitcher for the Diamondbacks.
"[Mock] has to be more consistent with his location. That's the final hurdle for pitchers who end up really good," Rizzo said. "The stuff is there. They show flashes of it, but the inconsistency kind of fights them every so often. That happens to a lot of young pitchers."
Rizzo calls Chico a great competitor, who goes after the hitters. Chico, 23, was 7-2 with a 2.22 ERA in 13 starts for Tennessee.
"He has no fear. He is the type of guy who really comes to the forefront in important situations," Rizzo said of Chico. "Along with his stuff, he has a four-pitch mix. His makeup and toughness on the mound really separates him from a lot of other pitchers."
Injury report: Right-hander Shawn Hill told MLB.com that he saw Dr. James Andrews in Birmingham, Ala., on Monday and there was no structural damage in his right elbow. Hill has been experiencing stiffness for several weeks, the last coming last week after pitching for Double-A Harrisburg.
According to Hill, the MRI showed some soft tissue problems inside the elbow, but it was not considered serious. Hill will return to Double-A Harrisburg on Tuesday, hoping to have a bullpen session in a couple of days and complete his 30-day rehab assignment. He hopes to return to the big leagues by September.
Hill started six games for the Nationals and is 1-3 with a 4.66 ERA.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.