In his first match at the 2020 ATP Finals, one of the two confirmed semifinalists, Daniil Medvedev hit probably the first underarm serve in the ATP Finals history.
The Russian was then of course asked about this act, and he emphasised that he was not trying to disrespect opponent in any way. Also Andy Murray and Gael Monfils, who are discussing moments from the 2020 ATP Finals on Twitch spoke about this moment, when they said:
“It’s quite interesting because always when that happens, the commentators and the pundits start going, ‘Is it disrespectful to hit an underarm serve?’… and I don’t understand it,” Murray said. “I don’t understand why that should be disrespectful if players are going to stand six, seven metres behind the baseline to return the serve. I think it’s a completely legitimate play and I think as we’ve seen, it actually has been at times pretty successful.”
“It’s not like players are doing it just to mess around or make fun of the opponent,” Murray said. “It’s used as a legitimate tactic when players are standing that far behind the baseline.”
“It’s also not that easy to do it," Monfils said.