Stuttgart, Germany, 8 June 2016 | AAP

John Millman has marched into the second round of the Mercedes Cup in Stuttgart after coming from behind to beat eighth-seeded Frenchman Lucas Pouille 6-7(3) 6-3 6-4.

The Queenslander will now face former US Open champion Juan Martin del Potro, who beat Grigor Dimitrov 6-4 6-2.

Millman joins compatriot Sam Groth in the second round; Groth saw off Illya Marchenko in his first match and will next line up against Dominic Thiem.

Local favourite and seventh seed Philipp Kohlschreiber saw off Pierre-Hugues Herbert of France 6-4 6-1, while Mikhail Youzhny of Russia beat fifth-seeded Spaniard Feliciano Lopez 7-6(3) 6-3.

Qualifier Florian Mayer defeated sixth-seeded Serb Viktor Troicki 6-4 7-6(4).

Troicki was the runner-up last season, when the tournament was still played on clay. It is now played on grass, as a tune-up for Wimbledon.

Troicki went down despite serving 10 aces. He lost his footing several times and produced a double-fault that allowed Mayer to serve out the match.

Mikhail Youzhny beat fifth-seeded Feliciano Lopez 7-5 6-3 and Taylor Fritz beat Fabrice Martin 3-6 7-6(6) 6-1 and will next play top-seeded Roger Federer, who had a bye into the second round.