Novak Djokovic has claimed that Gilles Muller's recent form means that his fourth-round opponent at the Australian Open has his full respect.

After battling injuries for long spells of his career, Muller has made an impressive start to 2015 to reach the fourth round of a Grand Slam for just the third time, and Djokovic is full of admiration for the 31-year-old.

"He struggled a little bit with injuries the last couple years, but I think the last six months has been playing some of his best tennis," the world number one told reporters.

"Now he's in the fourth round winning against some top players. Winning against [John] Isner in straight sets is never easy. He has done that. So he deserves respect. I need to be obviously very alert and hopefully I can return well, which is going to be one of the keys of the match."

Muller's only appearance in a Grand Slam quarter-final came at the 2008 US Open.