Alexander Zverev avoided a first-round upset at the Halle Open after battling past fellow German Oscar Otte on Tuesday.

The second seed managed to triumph in his first match since the French Open final defeat to Carlos Alcaraz, eventually winning 6-7 (5-7) 6-3 6-4.

Zverev has twice reached the show-piece at this event, in 2016 and 2017, though acknowledged challenges remain with adapting from the clay-court surfaces at Roland-Garros.

"A week ago, I was playing on clay still basically," Zverev said in his on-court interview. "He made it very tough for me, no rhythm at all.

"That's how grass-court tennis is sometimes and I'm just happy with the win.

"He did make it extremely difficult for me, so credit to him. I'm obviously happy that I won and hopefully, it's going to be a level above in the next match."

The world number four is now 35-10 for the season and will look to extend that record when he meets Italy's Lorenzo Sonego in the next round.

Zverev has won all three head-to-head meetings with Sonego, and will fancy his chances if he delivers another heavy-hitting performance next time out.

The 27-year-old smashed 54 winners, compared to his 40 unforced errors, to triumph in just over two hours under the OWL Arena roof.

Stefanos Tsitsipas also began his grass season with victory, defeating home hopeful Henri Squire 7-6 (9-7) 7-6 (7-2).

The Greek sixth seed will face Luciano Darderi or Jan-Lennard Struff in the second round.