Welcome back to the Monday Tennis Briefing, where The Athletic will explain the stories behind the stories from the past week on court.This week, a new tennis serve entered the canon, the first 2010-born winner emerged on the WTA Tour, and there was a historic meeting in São Paulo.If you’d like to follow our fantastic tennis coverage, click here.Serve overarm? Serve underarm? Why not both!The underarm serve has evolved from trickshot to tactic in the last decade, with big servers Alexander Bublik and Nick Kyrgios using it to exploit the deep return positions of their opponents. Some players who stand especially far back, including Daniil Medvedev, have been targeted even by players who don’t have a particularly big conventional serve.At the U.S. Open in August, Stefanos Tsitsipas took exception to Daniel Altmaier using the tactic and confronted him about it after losing their second-round match. And at last week’s Davis Cup qualifiers, an even weirder extension of the unconventional serve made a high-profile appearance. Playing for Hungary against Austria, world No. 154 Zsombor Piros produced the kind of serve hit by recreational players picking up a racket for the first time. He barely threw the ball up, and then patted it over to a disbelieving Lukas Neumayer on the other side of the net. Outfoxed, Neumayer couldn’t return the ball before it had bounced twice. He then looked to the umpire, hoping for some kind of intervention.