Troubled golfer Tiger Woods changed his mobile phone number five times in the past year, revealed a pro golfer pal.

In an interview with a US golf magazine, Mark Calcavecchia, 49, confessed that he even knew about a relationship Tiger had the year he married Elin Nordegren in 2004.

"I didn't really think about it, at the time but in the course of last year he changed his number five times," the Mirror quoted the golfer as saying.

"The last time he did, I said, 'Man, you change phone numbers more than I change underwear,'" he added.

Calcavecchia, 49, claimed he and Tiger would regularly exchange text messages until the scandal broke but said communication went cold when the 34-year-old had the infamous car crash.

"I did know of a girl he was seeing in Phoenix. I didn't know if it was before or after he was married. I knew it was close. It was 2004 sometime. I didn't think much of it then," he added. (ANI)