Novak Djokovic struggled to a three-set victory over Xavier Malisse at the Swiss Indoors in Basel.
World number one Djokovic beat the Belgian 6-2 4-6 7-5 in his first ATP match since winning the US Open in September, soon after which he suffered a back injury in a Davis Cup tie.
The victory takes his season record to 65-3 as he seeks a winning end to a year that has seen him claim three grand slams.
Djokovic didn’t expect to play at his full potential, but broke Malisse at the first opportunity.
Malisse fought back in the second and required treatment after colliding with the umpire's chair, but in the third the Serb closed out the final two games.
Mardy Fish's hopes of qualifying for the ATP World Tour Finals were dealt a blow after he retired from his first-round match with fellow American James Blake.