The charismatic English actor, who stars as the cocksure footballer Jamie Tartt, had to trust the writers to transform him from villain to hero.As Jamie Tartt in “Ted Lasso,” Phil Dunster began as a bratty showboat and is ending as an emotionally mature team player.Ryan Pfluger for The New York TimesThe new Jamie Tartt is very different from the old Jamie Tartt. As played by Phil Dunster, the 31-year-old English actor, the Tartt that closes out the third and probably final season of “Ted Lasso” is earnest, candid and emotionally mature — a far cry from the bratty, egotistic playboy and soccer star we were introduced to in Season 1.That Tartt was selfish and preening, a ball-hog on the pitch and a thorn in the side of those forced to put up with him, including his AFC Richmond coach, Ted Lasso (Jason Sudeikis); his professional rival turned personal trainer, Roy Kent (Brett Goldstein); and his on-again, off-again girlfriend, Keeley Jones (Juno Temple). Recent episodes of the hit Apple TV+ comedy have found Tartt opening up to those characters, among others, and learning to forgive his abusive father (Kieran O’Brien). Most surprising of all, he’s leading the Premier League in assists: The showboat is now a team player.In Wednesday’s finale — light spoilers start now — Jamie lands a Nike commercial in Brazil, shares a long-brewing heart-to-heart with Roy and visits his father in recovery, showing how much progress he’s made over the last three years.Dunster credited Jason Sudeikis, the star and co-creator of “Ted Lasso,” with helping him with his character’s evolution.Apple-TV+It has been a drastic reinvention for a character once known strictly for bad-boy smarm. And Dunster, faced with making this transformation convincing, had doubts that he could pull it off.“I was terrified constantly,” he admitted in a video call last week from his flat in London. “Every time I read a new script, I would think, [expletive], I don’t know how to do that.”He credits Sudeikis, as the star and co-creator of the series, with helping him through it, especially in a major scene in Episode 11 in which Tartt breaks down and weeps over the stress of an impending game before his hometown crowd. “There are some lovely things people have said after that episode, and the honest answer is that it was Jason’s idea,” Dunster said.Affable and boyish, with a thoughtful air that often had him gazing off into the middle distance before he spoke, Dunster seemed eager to look back on “Lasso,” as it drew to a close. (While no official announcement has been made about the show’s future beyond Wednesday’s Season 3 finale, there are currently no plans for more episodes or for spinoffs.) He reminisced about the casting process with a wistful glee, speaking in a tone of well-mannered English refinement that contrasts sharply with Jamie’s Manchester brogue.At the time, he said, the character of Jamie Tartt was called Dani Rojas, who was “what the character of Jamie is now, but maybe European or South American, representing where lots of footballers come from that might have a diva-y spirit.” (Dani Rojas later became a separate character, a soccer-loving Pollyanna from Mexico played by Cristo Fernández.)“It was easier to make him unlikable and trust the writing to show that he was redeemable,” Dunster said of Jamie. With, from left, Kola Bokinni, Charlie Hiscock and Cristo Fernández.Apple TV+Dunster auditioned “in a sort of Spanish accent,” he said, which was “not quite what they were looking for.” He assumed that was the end of it. But one afternoon some time later, while playing volleyball, Dunster got a call from his agent telling him that the producers wanted him back — only this time without the Spanish.“The note was, find an accent that would represent footballers in the U.K., that doesn’t sound like me,” he said. As a lifelong soccer fan, his mind went straight to Manchester — home of the vaunted Manchester United and the Premier League’s current juggernaut, Manchester City. Instead of “myself,” Jamie says “me-self”; “Keeley” becomes “Kee-lah.”“I did my best to make a fairly bold choice of who he was,” Dunster said. “It was a pretty broad brush stroke: a fame-hungry young man with a warped idea of celebrity who thinks longevity in this industry is to be as ostentatious as he can be.” He was careful, in the early going, not to soften Jamie’s harsher edges too much — he had to let himself be the bad guy, at least for a while.“It was easier to make him unlikable and trust the writing to show that he was redeemable,” he said. “It’s about getting out of the way of the text, isn’t it?”Brett Goldstein’s Roy Kent went from being Jamie’s rival to being his mentor.Apple TV+But his take on the character, informed by his deep soccer fandom, came to dictate much of how the character was written, he explained, right down to jokes that hinge on Dunster’s twanging accent. (One of the most memorable lines in Season 3 revolves around his singular pronunciation of a colloquial term for excrement.) Sudeikis encouraged the actors to “massage the text” so that it felt right for each of them, Dunster said, “whether that was to Anglify it, or Jamiefy it, whatever it needed.”Dunster, who grew up in Reading, England, was drawn to acting from an early age, appearing in school productions that won him much-sought attention in class and at home. “I don’t want to put it down solely to my performance as Oliver in a Year 3 production at school, but that laid the foundation of me being a show-off,” he said.Though he comes from a military background — both his brother and father served in the armed forces — he said his family supported his decision to pursue acting professionally by enrolling at the Bristol Old Vic Theater School. This was in part because, as he dryly explained, “they also knew I had zero academic skills, so they were like, ‘Yeah, mate, you’ve got nothing else going for you.’”After graduating, Dunster took a job as a waiter at an Asian restaurant in Brixton, but after a single trial shift, he could tell it wasn’t for him. “I flocked, man — I had someone who was looking after me, and I still managed to screw everything up,” he said. On the bus ride home, he was dismayed: “I remember thinking, ‘What am I doing? I can’t be an actor if I have to do this.’”Fortunately, he didn’t have to: He was offered a major role in the British period gangster film “The Rise of the Krays” (2015) almost immediately afterward, and just like that, Dunster went from anxious graduate to professional actor and has worked steadily ever since.Before “Ted Lasso,” Dunster won notice in “Murder on the Orient Express,” among other titles.20th Century FoxHe went on to earn notice with parts in the dark parenting comedy “Catastrophe” (2015-19) and in the Kenneth Branagh film “Murder on the Orient Express” (2017). But joining the cast of “Ted Lasso” in 2020 raised Dunster’s profile to new heights as the series became a pandemic-era phenomenon, wooing audiences and critics with its sweetly comic sincerity. Yet despite the show’s stratospheric stateside success, it has not gained a notable cultural foothold in Britain.“I’m constantly telling my friends, like, ‘Guys, I promise you I’m famous in America,’” Dunster joked. While he’s managed to persuade them to watch the show, the overall effect of its popularity on his career has been difficult to gauge.Dunster’s initial conception of Jamie was “a fame-hungry young man with a warped idea of celebrity.” In his real life, he tries not to worry about such things.Ryan Pfluger for The New York TimesOn the one hand, he said, “it’s slightly easier to come by meetings in America than here, which is not something I take for granted.” On the other, the whole notion of success and viewership at home versus abroad can be an unnecessary distraction.“It’s easy for that to be the focus rather than doing the actual work,” he said. “At the end of the day, the whole point of that stuff is to hopefully aid in me doing more interesting work.”“It’s an insidious thing,” he continued. “You can see it work its way through people — the desire to follow that stuff. It’s important not to fly too close to the sun, as some Greek dude once did.”“Ted Lasso” is above all a show about goodness — about finding the goodness in others and bringing out the goodness in ourselves. That includes Jamie Tartt, who Dunster said came to be “driven by love rather than driven by hate,” which he “never thought he would choose.” It’s perhaps unsurprising that his time on “Lasso” has taught Dunster the importance of “working with good people” — as the series wraps up, at least for now, that’s what he’s looking for again.“The part can be whatever — big or small, a nice guy or a bad guy, a prime minister or the opposite of a prime minister,” he said. “It doesn’t really matter, as long as the people making it are good.” More