Pitcher Jon Lester watches last Friday’s Red Sox-Orioles game at Fenway Park while leaning over the dugout railing.

AP / Charles Krupa

BOSTON — Ask Jon Lester when he thinks he’ll be ready to take the mound again for the Red Sox and he’ll tell you that he’s good to go today. No, make that yesterday.

The Sox’ organization is taking a decidedly more cautious approach to the lefty’s return, given what his body has been through over the last several months. And although eager to get back in the mix, Lester says he is, of course, fine with that decision.

“Since the season started, I’ve wanted to be here, but obviously they’ve got a plan and their biggest concern is my health, not only with my arm but with my overall health,” said Lester after last night’s game with the Tigers had been postponed because of rain.

Last year, the 23-year-old pitcher battled anaplastic large-cell lymphoma.

“I understand that — that they want to take it slow. Hopefully, this time we can do that without any problems, go from there and see what happens,” Lester said.

After getting off to a tremendous start with Boston last year, going 7-2 in 15 starts, Lester’s rookie season was cut short in late August when he learned that he had the treatable form of cancer.

After undergoing chemotherapy treatments, he was declared cancer free in December and was cleared to play baseball again this spring.

In late April, while he was on rehab assignment first with Class-A Greenville and then in Pawtucket, there was talk that Lester would replace Julian Tavarez in the starting rotation in the near future.

But those plans were quickly put on hold after a tough outing on May 2 at McCoy. Lester struggled through three innings against Indianapolis and made an early exit when he began experiencing some mild cramping in his left forearm.

The Sox brought Lester up to Boston after that so they could monitor him more closely as he worked with their training staff.

He began throwing again about a week ago and tossed another side session with Boston pitching coach John Farrell at Fenway Park before the rain started to fall yesterday.

“It felt good,” said Lester, who simulated pitching to three hitters. “Everything came out fine, just like we expected. We just wanted to make sure that later down the road that this doesn’t happen again and I’m out four to six weeks instead of two or three.”

Lester headed back to Pawtucket last night to rejoin the PawSox, and is expected to pitch at Ottawa in the first game of a four-game series against the Lynx on Saturday.

Francona said Lester will probably throw 50 to 55 pitches, but added, “He must be feeling good because he’s really fighting us on that. He’s ready to throw 100.”

“Hopefully, we can go 50, 60 on Saturday, then hopefully 60, 70 the next start, then maybe 80, 90,” Lester said. “Hopefully. We’re just trying to get through this one healthy, with no problems, and just keep getting stronger.”

Aside from the cramping that developed in that third inning on May 2, Lester says the difference between the way his arm feels now compared to last season is like night and day.

“I can’t even begin to tell you. I don’t have enough time. Really,” he said. “Just mechanically, I know where I’m at. I know what I’m doing. I know when the ball doesn’t go where I want it to go what went wrong and I can fix it. And it’s a good feeling. Last year, the wheels were spinning and I couldn’t figure it out, so it was tough.

“[Last year’s interim pitching coach Al Nipper] and I tried real hard to work out some stuff last year and saw some improvements, but then I’d take a couple steps back the next start,” Lester added. “So last year was just a battle from beginning to end.

“It could be because of what was going on with my body last year that the velocity wasn’t there, and the other half could be that my mechanics were off last year, and that’s why I wasn’t able to finish pitches like I’m doing this year with a little extra. So I’m feeling good all around right now.”

cthorn@projo.com