Phil Mickelson has never been one to hold back his thoughts, and on Sunday, as Scottie Scheffler led The Open Championship, Lefty decided it was time to clap back after being teased over an old comment.Earlier this season, Scheffler was coming off a freak palm injury sustained on Christmas Day and had gone winless in his first five starts.Around that time, Mickelson took a subtle jab while praising Joaquín Niemann's back-to-back LIV Golf wins on X. "Top 5 Try #1," the short and subtle dig aimed at the World No. 1 read.It followed another jab where Lefty directly targeted Scheffler, posting, "Here's a hot take: Does Scottie win in 2025 before the Ryder Cup? I don't think so," per Joel Beall's screenshot on X.Since then, Scheffler has flipped the narrative with wins at the CJ Cup Byron Nelson, the Memorial Tournament, and the PGA Championship at Quail Hollow.The LIV pro even acknowledged his misfire after Scheffler's PGA win in May. But the internet never forgets.On Saturday, after Scheffler's bogey-free 67 and Jim "Bones" Mackay's viral comparison of Scheffler to Tiger Woods, Kevin Kisner couldn't resist.He teased the 55-year-old on X posting, "Need the update!" on a screenshot that had Lefty's old comment.But Mickelson fired back with a lengthy reply that read."Kiz, my man. I've never been afraid to make mistakes on the course or off, knowing I'll have to deal with scrutiny from the public, media, or social media," he wrote. "I've already acknowledged I was wrong on this.This is a good example of why so many people are afraid to put themselves out there and compete or take risks because they know it'll be thrown back in their face and they can't handle it. Fortunately that's not ever been my problem. But others struggle dealing with the heat and scrutiny that professional sports and being in the public eye brings and drives many away from the game which is too bad but is reality for so many."Kisner later replied with a nod to Mickelson's own final round, where the 2013 British Open champion posted a bogey-free 67 to finish 1-over for the tournament.Mickelson, ever the showman, responded again."Thank you partner," he posted. "I believe you and I are still undefeated."Meanwhile, Scheffler opened his Sunday round with a birdie on the first hole, immediately reinforcing his grip on the leaderboard.With a four-shot cushion and momentum on his side, the World No. 1 looked poised to claim his fourth major title. With a win, Scheffler would become the 31st player with four or more major championship victories.More Golf: Lefty's Ex-Caddie in Awe, Makes Scottie Scheffler-Tiger Woods Comparison