Rafael Nadal says his confidence was boosted after comfortably beating Stan Wawrinka in his ATP World Tour Finals opener in London.
The world number five took advantage of an error-riddled display by the Swiss to win 6-3 6-2 and continue his late-season revival.
Nadal - who has won 14 of his past 18 matches following a disappointing third-round exit at the US Open - raced to victory with Wawrinka making 35 unforced errors.
The 14-time grand slam winner said he was feeling strong after getting off to the perfect start.
"I'm very happy to be back, the last year has been tough," the 29-year-old Nadal told the BBC.
"Without any doubt, this is one of the best tournaments in the world, in a great city. I'm very happy to start like this, that's important for my confidence.
"The last couple of weeks I've been playing well. I have the same motivation, the same spirit to keep improving my tennis."
Nadal will face Andy Murray on Wednesday.