The wait finally is over for Red Sox infielder Jonathan Diaz. After being taken in the 12th round of the 2006 MLB draft by the Toronto Blue Jays, the 28-year-old Diaz is making his major league debut against his former team on Saturday. To make room for Diaz on the roster, the Red Sox designated RHP Clayton Mortensen for assignment. “It’s an amazing feeling,” Diaz said before the game. “You can imagine something you work for your whole life. You actually get the opportunity to do it and it’s just very exciting.” Diaz signed a minor-league deal with the Red Sox in January before breaking camp with the Triple-A Pawtucket Red Sox. After a slow start with only four hits in the month of April, Diaz has turned it on of late, hitting .286 in May and June combined. “Baseball’s a hard sport so you just try to stay positive and you never know what’s going to happen, so I just try to keep my work ethic up and play hard,” Diaz said. Manager John Farrell considered that work ethic when deciding to put Diaz in the lineup, batting ninth and playing third base. In his two years as Toronto’s manager, Farrell had gained a familiarity with the infielder’s style of play. “This is a guy that’s worked probably seven to eight years to get to the big leagues,” Farrell said. “He’s a smart player and he knows what the expectations are of us.” Diaz echoed that sentiment.