Tom Selleck knows how hard it was to be Matthew Perry on "Friends."

That's because the "Magnum P.I." star had to channel Perry's famed Chandler Bing during a "Friends" episode in which Selleck's recurring character, ophthalmologist Richard Burke, starts acting like Chandler and Joey Tribbiani (Matt LeBlanc).

"We had this role reversal thing going, where (Richard) tried to be like them, and them like me," Selleck tells USA TODAY.

Selleck says he had trouble mastering Perry's famed sarcastic delivery for a Chandler-esque line about Richard's impressive foosball skills: "Could that shot be any prettier?" "Matthew had this speech pattern that I hadn't been aware of," Selleck says. The veteran actor sought frequent personal instructions from Perry.

Perry died on Oct. 28 at age 54.

"Matt told me: 'It's a joke, Tom. It's the way he says it.' But during that whole show, I kept going up to him asking, 'Can you say it again?' and he'd do the line," Selleck says. "That was his signature."

Selleck, 78, spoke to USA TODAY ahead of his return for Season 14 of "Blue Bloods."

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Selleck joined "Friends" in Season 2  as the handsome eye doctor who's two decades older than love interest Monica Geller (Courteney Cox) and good friends with her parents. Ironically, Selleck said his friendship with Perry's father, actor John Bennett Perry, helped break the ice with the tightknit cast.

"Everybody couldn't have been nicer to me," Selleck says. "But every day I'd see Matthew, and I'd ask him, 'How's your father?' And he'd always smile and we'd catch up. I got to know his father when I was a young struggling actor. Almost any commercial or pilot I went out on, there was John. We became real good friends."

The famously mustached Selleck portrayed Richard in nine "Friends" episodes from 1995 to 2000, working primarily with Cox. But Selleck particularly remembers the Season 2 episode "The One Where Old Yeller Dies," in which cigar enthusiast Richard starts morphing into Chandler and Joey − and vice versa.

Selleck recalls laughing with the studio audience when Joey and Chandler appeared in full Richard worshipping mode − Joey admiring his own cigar pose and Chandler entering with a faltering attempt at a Selleck mustache.

"(Perry) walked onto the set, and that brought the house down," says Selleck, who had no problem delivering Richard's later line: "Nice mustache, by the way. When puberty hits, that thing's really going to kick in."

Selleck praises the five-time Emmy nominee's acting chops. "He was raw talent. Matthew's gone, so it's easy to say this, but it's true. I think he was the most talented of a very talented group of people."

Selleck was touched to be invited to a private Los Angeles memorial service for Perry in October, attended by the "Friends" cast. But the "Blue Bloods" star was unable to attend because of his shooting schedule in New York.

The friendship between the "Friends" cast was real. "There are no bad stories. No star stuff. Nothing like that there," Selleck says. "You'd sit down to get notes on rehearsal, and it was fascinating. Courteney would be sitting on somebody's lap and then someone else's the next time. They all just got along. I think it's because all these actors had failures on other shows. And now they're in this hit. They all realized how lucky they were."