• "Friends" director James Burrows opened up about the show's cast members in his new memoir "Directed by James Burrows"
  • He revealed who he thought was the "most improved" and the cast member who "grew into" their humor
  • Burrows recalled mentoring David Schwimmer, who was a budding director at the time

"Friends" director James Burrows is opening up about his first impressions of the six lead stars of the beloved comedy series.

The prolific director, 81, revealed some insights on the cast of "Friends" — including who he thought was the "most improved" and the cast member who "grew into" their humor — in his upcoming memoir "Directed by James Burrows," an excerpt of which was published by WSJ. Magazine.

"I had a good sense about 'Friends' and knew two things immediately: one, I didn't have time to direct it, and two, I had to direct it. It became the last pilot shot that year," he wrote. "I fell in love with these six kids on the page immediately. Ninety-five percent of the original pilot script made it to air."

Looking back, Burrows said they had "amazing luck" because all six actors they wanted for the show were available at the time.

Discussing his impressions of its stars, the 10-time Emmy winner wrote that Courteney Cox, who played Monica Geller, "was not the funniest one in the group but grew into it and found her humor."

He suggested that the series could have been called "Monica's friends" because she was "the connection between the other cast members."

As for Jennifer Aniston, Burrows noted that she was "the hardest type to find in comedy" because the "Murder Mystery" actress is "both beautiful and funny."

While Burrows now considers Lisa Kudrow a "really good friend," he remembered hearing from someone on the show that the actress — who'd just lost the role of Roz in "Frasier" to Peri Gilpin — said, "'That f---ing Jimmy Burrows is directing the show. Can you believe it?'"

When it comes to their three male co-stars, Burrows singled out Matt LeBlanc, who played Joey Tribbiani, as "the most improved player."

"It's a tribute to his skills that his character developed over the course of the series. He never played Joey as the dumb guy, just as the incorrect guy, the 'much smarter than you think' guy, the one with the most growth potential, the least number of rules, and who became the most empathetic," said Burrows.

He noted that LeBlanc was able to evolve the role of Joey alongside the writers. "He grew the most, because he paid attention to all the notes and was the most willing to learn from the other five and from everyone else involved," Burrows continued.

Burrows also recalled mentoring David Schwimmer, who was a budding director at the time, and allowing him to shadow him on the sets of "Friends" and later "Will & Grace."

Schwimmer went on to direct 10 episodes of "Friends," other television episodes, a few movies and theater productions in Chicago and New York, according to the director.

"I once told him, 'Schwimmer, you're the second-funniest person I've ever known.' To this day, I've never told him who the first is," Burrows wrote.

Matthew Perry had what Burrows called a "very distinctive style" and was the "smart, quick one" on the show, according to the director.

"He brought the self-deprecating and the funny, good-looking guy to the table," he added of Perry.

"Directed by James Burrows" will hit the shelves Tuesday.

Cast members of "Friends" Jennifer Aniston, Courteney Cox, Lisa Kudrow, Matt LeBlanc, Matthew Perry and David Schwimmer
Cast members of "Friends" presenting the Best Supporting Actor and Actress for a Comedy Series at the 54th Annual Emmy Awards. Michael Caulfield/WireImage via Getty Images