Rafael Nadal had to recover from a set down against fellow Spaniard Fernando Verdasco before easing through to the second round of the bet-at-home Open in Hamburg.
Top seed Nadal, whose last appearance in the event was when he lifted the title in 2008, was playing his first match since his surprise second-round defeat to Dustin Brown at Wimbledon and he found it tough going initially.
However, after being broken twice to lose the first set to Verdasco, world number 10 Nadal hit back with a vengeance as he claimed a 3-6 6-1 6-1 win.
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Nadal's compatriot Roberto Bautista-Agut, the third seed, also progressed with a 6-3 6-4 win over Croatian teenager Borna Coric.
Bautista-Agut, who reached his fourth semi-final of the season in Umag last week, will now face Britain's Aljaz Bedene in the second round.
Slovenia-born Bedene saw off another Spaniard, Daniel Gimeno-Traver, 6-4 6-1.
Fourth-seeded Italian Andreas Seppi also tasted success on Tuesday, beating Martin Klizan 6-2 6-4, while sixth seed Juan Monaco of Argentina overcame Ernests Gulbis 6-3 6-7 (5/7) 6-3 in a testing opener for the 2012 champion.
It was not such a good day for seventh seed Guillermo Garcia-Lopez, though, as the Spaniard was forced to retire when 2-1 up in the first set against countryman Jaume Munar due to a leg injury.
Also, France's Benoit Paire, fresh of winning his maiden ATP World Tour title in Bastad, saw off home hope Philipp Kohlschreiber 6-3 3-6 6-1.