Andy Murray's former coach Ivan Lendl is working with Alexander Zverev ahead of the US Open.
Czech Lendl, an eight-time grand slam winner as a player, spent two separate spells working with Murray, helping the Brit to win all of his three major titles and reach number one in the world rankings.
The pair separated for the second time in November 2017.
Zverev is ranked fourth and has won 14 ATP titles, including three Masters 1000 events, but the 21-year-old has only reached the quarter-final stage of a slam once, at this year's French Open.
The German posted an image of a practice session ahead of the US Open to Instagram on Tuesday, accompanied by the caption, "Welcome to the team Ivan Lendl."
Zverev, who will be seeded fourth for the US Open, has not advanced beyond the second round at Flushing Meadows.