Roger Federer was far below his best when winning on Tuesday

Roger Federer overcame the loss of the first set against Belgium's Olivier Rochus to win his first-round match at the Estoril Open 4-6 6-3 6-2.

Rochus broke the world number one in the seventh game of the match thanks to two wonderful backhand returns down the line and a Federer double-fault.

But the Swiss superstar finally broke for the first time in the second set when Rochus sent a backhand wide.

Federer made errors in the deciding set, but ultimately won it comfortably.

His performance during the second half of the first set was particularly worrying in the first week of clay-court action of the year.

Rochus, the world number 77 who stands only 5ft 6in tall, forced Federer into long rallies and was frequently rewarded with mistakes from his more exalted opponent.

But Federer - whose serve (with 17 aces) was a vital weapon throughout - found a little more poise from the start of the second set and was rarely troubled after breaking Rochus.

606: DEBATE Federer's ground strokes leave a lot to be desired - he needs to win this event to get some sort of confidence back TheOpinion

That said, there was little to suggest that his new partnership with Spanish clay-court coach Jose Higueras would necessarily provide him with his first tournament success of the year.

"It was disappointing the way I played the first set but what can you do?", Federer said.

"You have to wake up in the second set and adjust a few things and in the third I started to get the upper hand from the baseline, which was key."

Earlier Russia's Nikolay Davydenko - Federer's main challenger in Portugal - breezed into the second round with a straight-sets win over Jurgen Melzer.

The number two seed and world number four beat his Austrian opponent, 74th in the world, 6-3 6-1.

Third-seeded Ivo Karlovic of Croatia retired injured while losing 6-4, 1-0 against Rui Machado of Portugal.