By Steve Keating TORONTO (Reuters) - Over the last three seasons finding a 10-game winner on the Pittsburgh Pirates pitching staff was like searching for buried treasure.

But not this season as Kevin Correia improved to 10-6 when the Pirates squeezed past the Toronto Blue Jays 7-6 on Tuesday to become the first Pittsburgh pitcher to record 10 wins before the All-Star break since Bob Walk in 1993.

Number 10 was hardly a gem as Correia served up five hits over six grinding innings, including home runs to Jose Bautista and Edwin Encarnacion but it was a milestone nonetheless for a team that has been the surprise package of the Major League season.

"This is not the easiest place to pitch with that lineup," Correia told reporters.

"There is no breaks in that lineup, every guy can hit the ball out of the park.

"These guys are looking to hit the ball out of the park and if they think they know what you're throwing they'll go down and get it.

"I just tired out, I didn't have a lot of easy innings."

The worst team in the Major Leagues last year winning just 57 games, the Pirates (40-38) are charging toward that total, moving two games above .500 to stay in the thick of the National League Central race.

Much of that improvement can be traced to Pittsburgh's starting pitching, which has gone from being the team's biggest weakness to one of their greatest strengths, ranked fifth in the NL behind pitching powerhouses Philadelphia, Atlanta, San Francisco and San Diego going into Tuesday's game.

In two of the three previous seasons, no Pirates pitcher had managed to reach double figures.

Zach Duke and Ross Ohlendorf each posted 11 wins in 2009 but last season and 2008 Paul Maholm was the ace of the Pirates staff with nine victories.

"It's better than not having 10 wins before July but not really, there is a lot of season left," said Correia, when asked if the 10 wins meant anything special. "Wins are nice but I'd like to keep it going."

The Pittsburgh bullpen has also proven sturdy, closer Joel Hanrahan coming on in the ninth with his team clinging to a one-run lead to get the final three outs and notch his 23rd save in 23 attempts.

It was the fifth win in six games for the surging Pirates, who also ended a 13-game interleague road losing streak dating back to June 2009.

The Pirates pitchers were made to work hard for the decision as the big-hitting Jays swatted four homers, Bautista slamming his major league-leading 24th of the season, while Encarnacion added a pair of solo shots and Corey Patterson another.

But Pittsburgh also showed plenty of pop at the plate, Andrew McCutchen finding the bleachers while Alex Presley hit his first career home run in his 2011 Pirates debut.

"I don't think I've ever been in a game up 6-1 and when it was over feel like we stole a win," said Pirates manager Clint Hurdle. "You don't throw good strikes they (Toronto) hit the ball out of the ball park.

"Kevin goes out there and competes, he does not back down.

"That has been one of the most impressive things about him this year. Whatever he's got he's bringing it to the table."

(Editing by Ian Ransom; To query or comment on this story email sportsfeedback@thomsonreuters.com)