Stanislas Wawrinka has revealed that he is pleased with how his body is responding despite losing in the semi-finals of the Sofia Open 7-6(6) 6-4 to Bosnia's Mirza Basic in his fifth competitive match in seven months.

However, he still needs more practice to get back to his best for which he is set to take part in the Rotterdam Open where he may be faced against compatriot Roger Federer, who is looking to take back the number one rank from Rafael Nadal after making a wildcard entry into the tournament.

The Swiss number two missed the second-half of last season due to a knee injury that required surgery. Wawrinka ended his 2017 season after his first round loss at Wimbledon and only returned to action at the Australian Open this year.

The 32-year-old lost in the second round in Melbourne but revealed that it was necessary for him to play to understand if his knee can sustain the pressure of playing competitive tennis.

Wawrinka was ranked world number three before being struck by the injury in 2017 and he is keen to get back to that level and start challenging for the major titles. However, he is willing to keep patience as his knee keeps improving and insists that he needs to keep playing competitive tennis, even if the results do not always go his way.

"It would have been great to win one more match but I need to take the positives from this week," Wawrinka said, as quoted by Reuters. "It was positive to have three matches in a row and win two matches. For sure it costs me more energy to win matches, since I am not used to play matches, but that is what I have to do to get back to my level.

"My knee's getting better," he added. "I am really happy and positive after the surgery, it has been six months until now and everything is going really well. I think I am doing everything possible to get back to what I want to be. I am moving well, I am playing well, but it is part of a process... to play more matches, to become more confident.

"There are a lot of things that you have to put together. It is not only about fitness, not only about tennis. It is also about being more relaxed while you play. Tomorrow I am travelling [to participate in the Rotterdam Open] and will try to practise there to prepare for my first match and to keep improving."