Diaz, 24, hit .285 with four homers, 11 doubles and 26 RBIs in 57 games in the Blue Jays' Minor League system. He started the 2008 season at Triple-A but has been hampered by injuries this season. He was put on the disabled list on May 3 with a right ankle sprain and missed almost two months of playing time while recovering.
After playing in 15 rehab games in the Gulf Coast League and six at the Class A level, Diaz returned to Triple-A Syracuse on July 24. He will now finish the season with Triple-A Indianapolis.
"In the word of some scouts, [he] can roll out of bed and hit .300," said Kyle Stark, the Pirates' director of player development. "Not a lot of walks, not a lot of power, but he can handle the bat. I think that, combined with the catch and throw skills, [make us] excited to have another quality Major League piece in the Minor League system."
Diaz was added to Pittsburgh's 40-man roster, effectively filling it back up to its maximum. Because he is on that active roster, there is a chance, too, that he could see playing time with the Pirates in September. The Pirates will almost certainly call up a third catcher for the final month of the season, and Stark said that Diaz is in the mix for that spot. Ronny Paulino would be the other possible option.
Diaz has been in Toronto's farm system since 2001 after being signed as a Minor League free agent out of the Dominican Republic after the 2000 season. He didn't play above Class A until last season, when he spent most of the season at Double-A before finishing the year with Syracuse.
Diaz has an average of .304 in 640 career Minor League games. He made a brief Major League appearance earlier this season, going 0-for-4 on April 23 before being sent back to Triple-A.
As for Bautista, the third baseman has gone 0-for-7 in three games since heading to Toronto, where he has taken on the role of everyday third baseman for the Jays.
Jenifer Langosch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.