Mickelson will play the St. Jude Classic, which starts Thursday, and then return to Bethpage Black for the U.S. Open. He is a popular figure in New York, and the runner-up to Tiger Woods at Bethpage in 2002.
He isn't sure what to expect from his game this week or next.
"I'm not playing just to play," Mickelson said, whose white cap featured a patch in the shape of a pink ribbon, the symbol of breast cancer. "Bethpage is a golf course that suits my game. I love that course. Obviously, I'm playing because I believe I can win. That's the goal."
Mickelson was at Bethpage on Tuesday for a practice round.
His voice cracked at times Wednesday while talking about his wife, Amy, one of the most popular figures on the PGA Tour.
He said the cancer was discovered early enough that she won't have to rush into surgery or make quick decisions. He expects surgery the first week in July, and only then will they have a better idea what they are facing.
Mickelson sounded as though he would play more than the U.S. Open. He just wasn't sure where.
"Throughout this year, we'll have a lot of treatment," he said. "We'll try to do normal things, like playing golf tournaments."
His three children are going camping with their grandparents this week, while Amy spends time with her closest friends. Mickelson said it was unlikely she would be at the U.S. Open - she rarely misses a major - because of the emotion.
"It's difficult to face a lot of people ... when you're seeing people crying," Mickelson said.
Mickelson has done his crying alone.
Supremely confident on the golf course, Mickelson said the emotions of watching his wife deal with breast cancer are new to him.
"I've never felt this emotion," he said. "I'll be driving alone and start crying. It's weird."
Golf has been part of their lives for the 16 years they have been together, and Mickelson is curious to see how he can separate a wife coping with cancer with the concentration required inside the ropes.
"I'm looking forward to the four to five hours ... where I'll be able to focus on something else," he said.
Copyright 2009 The Associated Press.