Former teammates Roy Halladay, left, and A.J.Burnett will put aside their friendship Tuesday when the Blue Jays and Yankees open a three-game series. (Adrian Wyld/Canadian Press)

For three years, A.J. Burnett was a sponge around Blue Jays ace pitcher Roy Halladay, marvelling at his work ethic, influence on teammates and pitching insight.

Little has changed now that Burnett toils for the New York Yankees, only the right-hander will be watching his mentor from the visiting dugout in his first return to Toronto after leaving as a free agent in the off-season.

Burnett and Halladay will go toe-to-toe on the Rogers Centre mound Tuesday starting at 7:07 p.m. ET in the opener of a three-game series between American League East Division rivals.

"I never expected that I'd match up against [Halladay] the first day back," Burnett, who declined a dinner invitation from the hurler and Blue Jays centre-fielder Vernon Wells on Monday's off-day, told reporters.

"We had a great relationship and I always wish him the best, except for Tuesday. He's going to be focused and so am I."

It hasn't been the best start in pinstripes for Burnett, who sports a 5.26 earned-run average in six starts as a Yankee. But he has remained healthy, something Burnett battled in his first two years in Toronto and previously with Florida.

In 81 games as a Blue Jay, Burnett had a 38-26 record and 3.94 ERA while striking out 231 batters in an 18-win season in 2008.

The competition between Burnett and Halladay — filled with jealousy early in their relationship — bonded the two pitchers, and they worked together and rooted for each other in their final days as teammates.

Mutual respect

As Burnett zeroed in on a five-year, $82.5-million contract with the Yankees after opting out of the final two years of his deal with Toronto, he was surprised to hear the effect he had on Halladay.

"It's funny, because when we parted ways, I told him: 'Thanks for everything. You've been a huge influence," Burnett said at spring training. "And he said: 'Thanks. I learned a lot from you, too.' I kind of laughed — 'What did you learn from me, dude?'"

With Burnett around, Halladay became less of a workaholic — or, in Burnett's words "an animal, five days a week.

"I went to [Toronto] for a reason," said Burnett. "I believe that reason was to be around a man like Roy Halladay. You see someone out there that's great and gets better every time. That kind of opens your eyes a little bit."

But there won't be any pleasantries exchanged after the first pitch Tuesday when the AL East-leading Blue Jays (22-12) look to build on their 5½-game lead over third-place New York (15-16).

The last time the Yankees paid a visit with Toronto atop the division standings was Sept. 24, 1993. The Blue Jays went on to win the second of back-to-back World Series titles that season, thanks in large part to a potent offence.

So far, the 2009 lineup is proving to be as strong, topping the AL with a .294 batting average and becoming the first team in the majors to score 200 runs (204).

Yankees hurlers getting lit up

It's enough to make a Yankees fan cringe, given New York has the second-worst ERA in baseball at 5.79.

"Let's go see what we can do. It all depends who pitches the best and who gets the timely hitting," said Blue Jays manager Cito Gaston after his club wrapped up a 3-2 road trip Sunday with a 5-0 win over Oakland.

Halladay kicked off the road swing with eight solid innings (one run) against the Los Angeles Angels to boost his record to 6-1 and lower his ERA to 3.29.

He is 15-5 with a 2.86 ERA in 32 career games versus the Yankees, including 5-1, 2.40 totals last season.

Burnett is coming off a no-decision against the defending AL champion Tampa Bay Rays in which he allowed three runs over six innings of work and fanned eight.

His only start against Toronto at Rogers Centre came in 2001 as a member of the Marlins.

On the injury front, Blue Jays pitchers Casey Janssen and Ricky Romero are scheduled to make rehabilitation starts Tuesday and Wednesday, respectively, for the double-A New Hampshire Fisher Cats.