Tim Henman suffered a straight-sets defeat against Croatia's Ivan Ljubicic in his first competitive match for over three months.
Henman did not have a happy return to action
The British number one lost 6-4 6-2 in the first round of the World Indoor Tournament in Rotterdam.
Henman, seeded fifth, was making his return to the circuit after undergoing surgery on his right shoulder in November.
Ljubicic, the world number 52, came into the match on the back of an impressive display in Croatia's Davis Cup win over the USA.
The pair had met only once before, with Henman winning comfortably at the semi-final stage of the same tournament last year.
But the Briton was quickly in trouble this time, dropping his first two service games as the first set slipped away.
And Ljubicic kept the pressure up with a barrage of heavy serves and returns, firing 13 aces - five on second serve - and 13 return winners.
Mentally my focus was 75% on my shoulder
"He served phenomenally well," said Henman.
"It felt most of the time he was hitting two first serves which I guess happens when you grow up watching (Goran) Ivanisevic."
Ljubicic broke again in the fifth and seventh games of the second set on his way to closing out the match, with Henman unable to cope on his return to match play.
"I felt pretty pleased with the way my shoulder felt in my first match (after such a long time)," said Henman afterwards.
"Mentally my focus was 75% on my shoulder and when you're competing at this level, you've got to be thinking about the tennis rather than something like that.
"Tennis at the highest level is about confidence and I know it will take time to get that back."
And despite the result, Henman was determined to look only at the positives.
"I always want to win but I have to look at the bigger picture and if it takes me six months to get back into form then so be it," he said.
"From the middle of August last year till the end of the season, I played in pain and that's not much fun.
"Although I don't enjoy losing, it just felt good out there to play pain free."