Roger Federer continued his resurgence at the Monte Carlo Masters with a battling victory over David Nalbandian on Friday.

The world number one, who has struggled with form and fitness this season, looked completely out of touch on Wednesday when he had to battle back from a 5-1 final set deficit against Ruben Ramirez Hidalgo.

He looked more composed against Gael Monfils on Thursday and was close to his best against Nalbandian, who had won their two previous meetings in Madrid and Paris.

Although he dropped the first set, the Swiss stormed back to clinch a 5-7 6-2 6-2 victory and a place in the semi-finals.

The opener was decided by a solitary break of the Federer serve in the 11th game but, after the players traded breaks at the start of the second, Federer struck again to establish a 4-2 lead.

A further break set up a deciding set.

Nalbandian was still holding his own from the baseline but Federer's greater variety gave him the edge. The Swiss broke twice more in the third set to go through to a meeting with either Australian Open champion Novak Djokovic or Sam Querrey.

Afterwards, Federer was pleased to have played so well against the Argentinian.

He told Sky Sports 2: "I have played some good matches this season but clay courts are a different proposition.

"Playing against David is always fun, we go way back. It was a good match and I am happy with the way I played.

"It was another tough match but I am strong physically."

Nikolay Davydenko was the first man into the last four after edging his way past Russian compatriot Igor Andreev.

The fourth seed, chasing a second successive Masters Series title following his victory in Miami, won 6-3 4-6 7-5.

Federer Marches On