Juan Martin del Potro makes his return after one month away with wrist problems as top seed at the ATP Vienna Open starting on Monday.
The Argentine, who lost the title match a year ago to Frenchman Jo-Wilfried Tsonga, has been absent since winning his only match in the Davis Cup semi-finals last month against the Czech Republic.
Following that win over Radek Stepanek, Del Potro never played again during the weekend after aggravating his left wrist in what turned out to be an ill-advised victory.
He needs to play catch-up if he is to have a chance of qualifying for next month's season-ending World Tour Finals in London, an eight-man event with four spots remaining open.
De Potro currently stands provisional seventh behind Tomas Berdych and Spain's David Ferrer.
While he has been out of action, it's been just the opposite for second seed Janko Tipsarevic.
The Serb has been an action man over the past few weeks in Asia, where he won the first title of his career a year ago in Kuala Lumpur.
Tipsarevic played the Bangkok semis, made the quarters last week in Tokyo and reached the third round at this week's Shanghai Masters, where he lost to Tommy Haas.
The German, once second in the world, takes the third seeding at the Stadthalle. He is fresh from a few days of rest in Dubai after a Shanghai quarter-final.
The 34-year-old qualified into the Vienna field a year ago and progressed to the quarter-finals, where he ran into Del Potro.
Haas first played Vienna in 1997, a decade and a half ago, and won the title four years later.
The first four seeds all have byes into the second round, where Del Potro will play a qualifier and Tipsarevic faces either wild card Ernests Gulbis of Latvia or Indian Somdev Devvarman.
Austrian Juergen Melzer, winner of the title in 2009-2010, will hope to be over his run of recent injuries which led to first-round defeats at the US Open, Kuala Lumpur and in Shanghai.