SCOTTSDALE, Ariz. — In the biggest winter of his professional life, after a third despairing season of high earned-run averages and low success, Tim Lincecum turned to the man who taught him how to pitch, and it started with an apology.

Sorry, Dad. Sorry I pulled away from you when you were trying to help me. Now, let’s fix this.

That was the tenor of the conversation Lincecum said he shared with his father, Chris, before they embarked on an offseason of rediscovery and about 50 throwing sessions in Seattle.

They worked to refine the complex delivery that twice made Lincecum a Cy Young Award winner, and also led to his downfall over the past three seasons because of his inability to understand why he could not fix it.

“My dad knows my mechanics better than I do,” Lincecum said Wednesday as pitchers and catchers reported to spring training at Scottsdale Stadium. “He’s always been the one who kind of reaffirmed and reignited that idea of 'our mechanics.’ I lost grasp of that over the past few years trying to do it myself.”

The Giants’ 30-year-old right-hander was exceptionally candid as he began a critical spring. Earlier in the day, manager Bruce Bochy all but said Lincecum will be the fifth starter, with Ryan Vogelsong and Yusmeiro Petit opening the season in the bullpen and spot-starting if needed.

If Lincecum cannot reverse course after posting ERAs of 5.18, 4.37 and 4.74 the past three seasons, and losing his rotation spot late last summer, he will enter free agency as the “once great pitcher who lost it.”

Lincecum said the way 2014 ended — in the bullpen, worthy of one garbage-time appearance in the postseason — motivated him to do what he called a “180-degree flip” and undertake a rigorous offseason throwing program under Chris Lincecum’s direction.

“I feel I’ve got to re-earn my spot in the rotation,” Lincecum said. “I didn’t finish the year that well at all. It kind of left a drive in me to get back and find out what went wrong.”

He felt his father held the key. Lincecum had to swallow a big gulp of pride when he approached Chris for help after three years of pulling away professionally and personally.

As Lincecum struggled over the years, his father would quiz him on each bad outing, and that began to chafe. It got “old and tedious,” Lincecum said.

When he approached his father about working together, Lincecum had to admit that he needed the help and said the apology and his dad’s acceptance made for an emotional moment.

“I went to him. That was tough,” Lincecum said. “It’s like a kid with a bad report card going home to his dad and saying, 'I tried to do it on my own.’ They’re there to remind you that it’s never going to be that way.

“I needed the help. It was definitely freeing to be able to say that to him, and him understanding where I was coming from. We came together pretty quickly after that.”

So Tim threw, and Chris watched and critiqued. More than that, the elder Lincecum explained the reasoning behind each mechanical “bullet point” in ways the pitcher had not understood as a kid.

Lincecum admitted he sometimes stubbornly refused to listen.

“Those moments came out where he had to go take a smoke break and I would just be throwing into a net by myself,” Lincecum said. “That happened quite a bit. We learned to love each other regardless and move on, knowing we’re both fighting for the same thing.”

Lincecum said he now feels the ball coming out of his hand better and more efficiently, as he put it, not having to expend 150 percent effort to get a 60 percent result.

If he falters in Arizona, he will be able to turn to his dad for advice.

Chris Lincecum will spend the next month in spring training, offering words that his son is ready to hear.

Henry Schulman is a San Francisco Chronicle staff writer. E-mail: hschulman@sfchronicle.com Twitter: @hankschulman