Two-time BMW Open champion Alexander Zverev is hoping to enjoy further success in Munich after shaking off the rust in his opener on Wednesday.

Zverev has been managing an elbow injury and had only played three times since mid-March, swiftly departing Masters 1000 events in Miami and Monte-Carlo.

But the German is back in familiar territory on home soil and made light work of lucky loser Ricardas Berankis.

Zverev, who won the tournament in 2017 and 2018, needed just 87 minutes to claim a 6-2 6-4 victory.

"I haven't played much tennis the past few weeks, so I know I'll need to improve for the next match," he said.

"I've had success in the past and I feel good here. I've played well in the practice and hopefully I can do better on the match court."

Fellow seeds Casper Ruud and John Millman each also advanced, albeit the latter only when Guido Pella retired after the Argentine won the first set 6-4 and was 2-0 down in the second.

At the Estoril Open, Marin Cilic and Kevin Anderson will face off in an enticing quarter-final.

One-time US Open champion Cilic has a 6-1 career lead over Anderson, who has fallen to 105th in the world.

Cilic came from behind to beat Nuno Borges 6-7 (5-7) 6-4 6-4, while Anderson defeated Roberto Carballes Baena in straight sets.

Alexander Bublik's status as the Estoril Open's fifth seed meant little to Pedro Martinez as the Spaniard romped to victory.

Qualifier Martinez needed just 53 minutes to see off a player ranked 57 spots above him, triumphing 6-3 6-0 to reach the second round.

He will now face Cameron Norrie, a 6-1 6-3 winner over home hope Joao Sousa in Portugal.

Marin Cilic, himself seeded sixth, might have feared going the same way as Bublik after a chastening second set against 17-year-old Carlos Alcaraz.

But the Croatian held his nerve and got the job done in a 6-3 1-6 6-4 success.

Finally, fellow seed Albert Ramos-Vinolas was relatively untroubled in overcoming compatriot Fernando Verdasco 6-3 6-3 in an all-Spanish clash.

At the BMW Open, Jan-Lennard Struff secured safe passage to the second round on home soil in Munich.

The German saw off lucky loser Andrej Martin 6-4 6-3 and the seventh seed now face Dominik Koepfer, who downed three-time champion Philipp Kohlschreiber 4-6 6-4 6-3.

Elsewhere in the draw, Nikoloz Basilashvili, seeded fifth, defeated Thiago Monteiro, while the sixth-seeded Dusan Lajovic suffered a straight-sets loss to world number 127 Mackenzie McDonald.

John Millman outlasted Alexei Popyrin in a near three-hour marathon to progress to the second round of the BMW Open.

Eighth seed Millman was made to work exceedingly hard to avoid an early exit, eventually coming through a contest in which the two Australians faced a combined 31 break points by a 7-6 (7-3) 3-6 7-5 scoreline.

Ricardas Berankis won a 22-point tie-break in the first set to defeat Maximilian Marterer, while there were also wins for Millman's next opponent Guido Pella, Federico Coria and Ilya Ivashka.

At the Estoril Open, Kevin Anderson saved a match point at 6-5 down in the second set tie-break and turned around a 4-1 deficit in the third set to beat Frances Tiafoe 4-6 7-6 (8-6) 7-6 (7-4).

"It was obviously a very, very close match," Anderson said. "I think there were a lot of positives, a lot of really high-quality tennis, especially from midway through the second until the end of the match, I was really happy with the way I played.

"I think even if I had lost that match, obviously it's always tough losing, but I definitely felt I took a step in the right direction.

"Getting the win is a big added bonus, it gives me another opportunity to come out in a couple days' time."

Eighth seed Alejandro Davidovich Fokina beat Pablo Andujar in three sets, with Jeremy Chardy and qualifier Nuno Borges also victorious in Portugal.