Andy Murray was not at his best against Rafael Nadal in his second group match of the ATP World Tour Finals in London on Wednesday, going down to the Spaniard in two tame sets.

While that loss was disappointing to take for the Brit, Murray lost his cool, something he rarely does, when a journalist suggested he might have played below par against Nadal in order to avoid a potential semifinal against Novak Djokovic.

Two players from each of the two groups will qualify for the semifinals, with the winner of the Ilie Nastasic Group, Murray and Nadal's, taking on the winner of the Stan Smith group and vice versa.

Djokovic was fancied to win his group comfortably, considering his form, but that fell by the wayside after his straight-set loss to Roger Federer on Tuesday. That means Djokovic is now likely to finish second in his group, meaning the Ilie Nastasic group winner will probably face the world number one, who has been near-unbeatable in 2015, in the semifinals.

Murray, though, insisted he wasn't even remotely thinking along those lines en route to his 6-4, 6-1 loss to Nadal.

"I don't think that's a question, that's your opinion," Murray said when a journalist put that question. "You're basically telling me that the format is wrong.

"I think that Roger plays great in this event. He's won it, what, six times, played some unbelievable matches here. He obviously played great tennis [when he beat Djokovic in straight sets].

"This isn't for me about who's better out of Roger and Novak because things can change on a daily basis. Obviously I lost comfortably to Rafa and I could play him in a couple days' time and it could be a different story.

"I'm sure Novak feels the same way about his match with Roger. I think all of the players know that. I'm not trying to finish second in the group. I'm trying to win every match I play. I hope that's how all of the players view it. Some people might have different opinions.

"That's fine if you have a different opinion to me. I don't think it's right to tell me that the format is wrong, that I would rather finish second than first, when that's not true in my mind."

For Murray to even finish second, he must beat Stanislas Wawrinka in his final group match on Friday. Wawrinka, after a forgettable performance against Nadal in his first match, beat David Ferrer 7-5, 6-2 on Wednesday.