Ivan Lendl explains reasons behind Andy Murray's dip in form

Andy Murray's dip in form was down to illness and injury, according to his coach Ivan Lendl.

From hugely unpromising beginnings, the world No. 1 has progressed through the French Open draw to another Grand Slam semifinal.

He will face Stan Wawrinka on Friday looking to repeat last year's victory, which earned him a first final appearance at Roland Garros.

Lendl has reunited with Murray for the first tournament since the Australian Open having watched his charge's struggles from afar.

Lendl said: "Obviously winning is better but I knew the reasons why he is struggling. It was just a bit of bad luck.

"With the shingles and the elbow and then flu and then another flu and so on and so on. You just need to put in consistent work before you can expect consistent results.

"He's won five matches and I'm hoping he can win one more tomorrow."

Murray and Lendl got back to basics in the week before the tournament -- once Murray had got over his latest illness.

The Scot admitted the drills were "pretty boring" but they have had the desired effect, with Murray now resembling the player who dominated the second half of last season.

He said: "When I'm getting into longer rallies now, I feel like I'm sort of in autopilot a little bit, like I know what I should be doing, and I'm hitting the ball in the right place.

"Whereas in Madrid [where he lost his second match to Borna Coric], I didn't know which shots to play. I was rushing a little bit in long rallies. I was making poor decisions.

"So I'm thinking less on the court. I think when things aren't going well, it's very easy to overthink things. You can be worrying about technique, which is never good when you're playing matches.

"I was still feeling a little bit like that at the beginning of the tournament, the first match. But I got through that and that made a huge, huge difference to me."

That first win was against Andrey Kuznetsov, and further victories have followed against Martin Klizan, Juan Martin del Potro, Karen Khachanov and Kei Nishikori.

Murray's quarterfinal against Nishikori will certainly not be remembered as a classic, with windy conditions making finding a rhythm difficult for both men.

Murray will almost certainly have to play better if he is to repeat last year's victory over Wawrinka, who is yet to drop a set and crushed in-form Marin Cilic on Wednesday.

Murray said: "When we played last year, it was a similar situation coming in. I think Stan had played really well.

"I had struggled in some of my matches during the event last year, but I played one of my best clay-court matches that day to get the win. I need to do the same again tomorrow.

"He's obviously played extremely well the last few years at the French, and he's confident. It's going to be very tough.

"But I can learn some things from last year. I'm sure he will, as well, and will try to change some things. It should be an interesting match."