TORONTO -- One of the most important days this season for Shaun Marcum's came when the Blue Jays didn't even have a game. An off-day on June 14 allowed Toronto to slot the young starter behind Roy Halladay in the club's rotation.

Since then, Marcum has followed Halladay on 12 occasions, including 10 times against the same opponent. When Marcum is set to start in the same series as Halladay, the 25-year-old has been paying close attention to how Toronto's ace approaches batters, and it's been working.

"I kind of like pitching behind Doc," Marcum said on Wednesday. "I can see how he goes about facing the hitters, especially when it's the same team. You can see how he handles the hitters and how he prepares for them. That helps me out."

It's especially beneficial for Marcum, because he uses a style similar to that of Halladay. Both right-handers attack the strike zone with a pitch-to-contact approach that's designed to create quick outs. Since that off-day in mid-June, Halladay has turned in six quality starts. Marcum has followed suit each time he's taken the mound in the next game.

The latest example came on Wednesday, when Marcum limited the Angels -- a club he'd never faced in his career -- to one run on four hits over seven innings. On Tuesday, Halladay turned in his fifth complete game against Los Angeles, which managed only five hits off the 30-year-old righty, who won the American League Cy Young Award in 2003.

"You just want to go out there and keep doing what the guy in front of you is doing," said Marcum, who is 9-2 with a 2.91 ERA in 18 starts this year. "Doc threw really well [on Tuesday], so I wanted to go out there and do what he did and keep our team in the game."

It goes both ways, too. In consecutive starts from July 6-12, Halladay combined to go 1-1 with an 8.44 ERA in outings against the Indians and Red Sox. In the following games against Cleveland and Boston on July 7 and 13, respectively, Marcum combined to go 1-1 with a 10.61 ERA.

In the eight other starts against teams Halladay faced the day before, Marcum has gone 4-1 with a 1.98 ERA. That's slightly better than the 2.93 ERA Halladay has posted over that same span. Marcum ranks second to Halladay on Toronto's staff with 14 quality starts, including nine in the 10 games he's followed the ace in the same series.

Chacin update: On Thursday, Blue Jays general manager J.P. Ricciardi said that the club is leaning toward having injured pitcher Gustavo Chacin undergo surgery on his left shoulder before the end of the season. Chacin has been on the disabled list with the arm ailment since April 28.

"We're trying to find out if we need to have exploratory surgery in his shoulder," said Ricciardi, who added that the only throwing Chacin might do over the next few weeks would simply consist of light rehab work. "He's probably going down that road."

"We've done everything we possibly can do and we're getting to a different stage now," Ricciardi added. "We just need to take a different course. When you exhaust all the things you're supposed to do and it doesn't work out, you've got to try to find another [option]."

Chacin, 26, went 2-1 with a 5.60 ERA in five April starts this year for the Blue Jays, but he's fought various arm injuries over the past two seasons. In parts of four seasons with Toronto, the Venezuelan southpaw has gone 25-15 with a 4.18 ERA in 58 stats.

Power outage: The Blue Jays' lineup is built for power, but there's been a considerable lack of pop this month. Entering Thursday, Toronto had launched a total of four home runs in August -- the lowest output in the Majors. Then again, the Jays have tallied 39 doubles this month, which was the second-highest total in baseball.

In fact, the 258 doubles that the Jays carried into Thursday's tilt against the Angels ranked first in the AL. In the fifth inning on Wednesday, Matt Stairs led off the inning with a double, giving Toronto at least one in each of the past 22 games, marking the longest active streak in the Majors.

League watch: Toronto manager John Gibbons said that right-hander Brandon League played long toss prior to Thursday's game. On Sunday, League was placed on the 15-day DL, retroactive to Aug. 5, with an oblique strain. There's currently no established timetable for League's return to the bullpen, but the pitcher is eligible to be activated during the upcoming home series against Oakland.

One too many: On Wednesday night, the Blue Jays took a 2-1 decision over the Angels, giving Toronto its 21st one-run victory of the season -- tied for the most such wins in the AL. The Jays upped their record this year to 21-19 in one-run affairs (13-4 at home and 8-15 on the road). The 40 one-run contests are the most of any club in the league.

Did you know? Entering Thursday, Marcum's 2.91 ERA out of Toronto's rotation ranks third in the AL among pitchers with at least 18 starts. Dan Haren (2.53 ERA) of the A's and Kelvim Escobar (2.74 ERA) of the Angels rank first and second, respectively.

Quotable: "Our Gulf Coast League team has more home runs than us." --Ricciardi, joking on Thursday about Toronto's lack of home runs this month

Coming up: Toronto right-hander A.J. Burnett (6-6, 4.09 ERA) is scheduled to take the mound when the Blue Jays host the Orioles at 7:07 p.m. ET on Friday at Rogers Centre. Baltimore will counter with left-hander Garrett Olson (1-1, 4.60 ERA).