The world number four, who before this week had not played on the ATP tour since September’s US Open, dropped a set against little-known Argentine Leonardo Mayer in Thursday’s second-round but looked back on top form against Montanes, ranked 34.

He broke serve four times on the way to winning the first set and opening a 4-0 lead in the second and wrapped up the match with a forehand winner.

‘My wrist is still giving me some pain but I am feeling better every day,’ Murray said at a news conference at the Spanish hardcourt event. ‘I played well today and tomorrow I hope to improve even more.’

The Scot will play Fernando Verdasco in Saturday’s semi-finals after the Spanish fourth seed nailed a slew of crashing winners to brush aside compatriot and seventh seed Tommy Robredo 6-3 6-2.

Verdasco’s win and a victory earlier on Friday for Russian second seed Nikolay Davydenko means they both remain on track to secure the remaining two places at the World Tour Finals in London later this month.

Roger Federer, Rafael Nadal, Novak Djokovic, Andy Murray, Juan Martin del Potro and Andy Roddick have all qualified for the Nov. 22-29 season-ending event and Davydenko holds seventh spot and Verdasco eighth.

Davydenko beat Guillermo Garcia-Lopez 6-4 7-6 and will contest a place in Sunday’s final with compatriot Mikhail Youzhny, who maintained his dominance over Gilles Simon by beating the French fifth seed 6-4 6-4.

Youzhny saved all 11 break points he faced and it was his fifth victory in five meetings between the pair.

Verdasco’s win ended both Simon’s and Robredo’s hopes of securing a place in London.