Roger Federer is wary of Nick Kyrgios and his cannonball serves as Team Europe look to preserve their unbeaten record at the Laver Cup this weekend.
The third edition of the new annual teams' event gets under way in Geneva on Friday with Federer and Rafael Nadal once again spearheading Team Europe against Kyrgios and company's Team World.
Team World's top-ranked player, world No.20 John Isner, is under no illusions as to the enormity of his side's challenge, branding the star-studded opposition as "the greatest team of all time".
Federer, though, is on guard, mindful of the threat that Isner, Kyrgios and the supersonic serving of former Wimbledon finalist Milos Raonic pose in the shortened format.
Federer and Nadal will be joined in Team Europe by fellow top-tenners Dominic Thiem, Alexander Zverev, Stefanos Tsitsipas and the 11th-ranked Fabio Fognini, with Taylor Fritz, Denis Shapovalov and Jack Sock rounding out Team World.
"We have incredible depth," Federer said.
"The problem is we are indoors, best of three (sets), super-tiebreaker in the third, and we are playing against big servers who like the indoors and all have a big forehand.
"So as much as we are the favourites, I do think it's going to be extremely tight. They are really good at doubles.
"Obviously Jack I think is one of the world's best doubles players if not the absolute best right now.
"We know how hard it's going to be."
As usual, the format is three singles and one doubles match on each of the three days.
But to ensure the tie can't be decided until Sunday, one point is awarded for each rubber won on day one, two points for each match won on day two and three each on Sunday.
Federer saved a match point against Kyrgios in clinching a 15-9 victory for Team Europe in the final match of the inaugural Laver Cup in 2017 in Prague.
Last year was again tight, with Team Europe prevailing 13-8 in Chicago but only after saving match points in an incredible four rubbers.
"We are obviously big underdogs but we have been close, very close, so we feel confident that we can pull off an upset," said Team World captain John McEnroe.
"But of course we know that obviously a couple breaks could hopefully go our way. When you have four matches, you have match point and lose all of them, that's rough, especially when you're playing guys this good.
"So hopefully we will take advantage of those chances."
TEAM EUROPE: Rafael Nadal (world No.2), Roger Federer (3), Dominic Thiem (5), Alexander Zverev (6), Stefanos Tsitsipas (7), Fabio Fognini (11). Alternate: Roberto Autista-Agut (10).
TEAM WORLD: John Isner (20), Milos Raonic (24), Nick Kyrgios (27), Taylor Fritz (30), Denis Shapovalov (33), Jack Sock (210). Alternate: Jordan Thompson (53).