After a disastrous start to his Australian campaign, French veteran Gilles Simon says he’s finding fitness and form in time to challenge for the first grand slam title of 2015.

At the Australian Open warm-up tournament at Kooyong on Thursday, the world No.20 cruised to a straight-sets win over young Serb Filip Krajinovic 6-4 6-3.

It was a big improvement on his first-round drubbing at the Brisbane International when he was humbled by Australian wildcard James Duckworth 6-2 6-2.

Simon said he had been struggling with lower back and knee complaints which weren’t helped by the long flight down under.

“It has been difficult for me since I came to Australia as physically I was not in good shape,” the 30-year-old said.

“It was really hard for me to move and the match in Brisbane was a disaster … but I feel better than before.”

Simon had an impressive finish to 2014, losing in the fourth round of the US Open in five sets to eventual champion Marin Cilic and then making the final of the Shanghai Masters, where he bowed out in two tiebreak sets to Roger Federer.

Such performances give Simon, a former world No.6, belief that he’s still capable of winning a grand slam.

“If I won Shanghai it would have been the best result of my career,” the father of two said.

“When I’m able to run I will be hard to beat for anyone, even for the really top guys.

“I’m a bit disappointed I couldn’t beat one of the top four last year because I had chances against every one of them which means my level can be really high when I’m in good shape.”

Meanwhile, promising young Australian Jordan Thompson continued his run of impressive form, taking the scalp of world No.14 Feliciano Lopez.

Thompson won 7-6 (9-7) 6-3, a day after pushing world No.5 Kei Nishikori to three tight sets.

The world No.273 used his speed and serve to outplay 33-year-old Lopez.

“I played really well today,” the Sydneysider said.

“He didn’t play his best but I will definitely take that.”

The win was a big boost to Thompson’s confidence heading into the Australian Open, where he will be the beneficiary of a wildcard for the second straight year, courtesy of his victory in December’s playoff.

Alex Dolgopolov from Ukraine takes on Spaniard Fernando Verdasco in the Kooyong Classic final on Friday, while Frenchman Richard Gasquet and Nishikori will play off for third place.