Martin Klizan was locked in a tense battle with Paul-Henri Mathieu at the Moselle Open until his French opponent had to retire due to injury.

Sixth seed Klizan had recovered from losing the opening set in Tuesday's first-round clash in Metz to level at 6-7 (1-7) 6-3.

The Slovak had just broken for a 3-2 lead in the third set, but there would be no chance for 2008 runner-up Mathieu to recover as he pulled out with an Achilles injury.

Vasek Pospisil is the next opponent for Klizan after he comfortably saw off the challenge of Aleksandr Nedovyesov 6-1 7-5.

The seventh and eighth seeds Adrian Mannarino and Fernando Verdasco faced differing fortunes in progressing to round two.

Mannarino was a comfortable 6-2 7-5 victor over qualifier Vincent Millot, while Verdasco had to come from behind to beat Alexander Zverev 6-7 (2-7) 6-3 6-3.

Edouard Roger-Vasselin set up a second-round clash with second seed and two-time champion Gilles Simon after beating French compatriot Kenny de Schepper 6-4 7-6 (7-2).

Rounding off the action, Mischa Zverev - the 2010 runner-up - was taken the distance by Pablo Carreno Busta in a 6-2 6-7 (3-7) 6-1 win.