However she has already shown in Rome an ability to raise her game when needed, an attribute she is likely to have to call upon at this month's French Open. "I don't get frustrated because I have to think I've had a long time off," she said. "I definitely felt extremely rusty today.
"It went crazy in the second set. I was glad I was able to win because at least I can be guaranteed another match. I think I definitely need it because I was definitely rusty." "But that's the great thing about playing matches (rather than just training) and I was glad to win because you're guaranteed another match and I need it because you could see today I was rusty."
However she insisted that she is already in better shape ahead of the French Open than she was last year when she lost in the quarters to eventual winner Svetlana Kuznetsova. Last year she lost in her opening match in three successive clay events leading up to Roland Garros. "I'm better than I was this time last year. I lost in the (second) round (after a first round bye) and wasn't doing so well. "My goal is to do better than last year and so far it's going well."
Serena looked comfortable in the first set, reading her opponent's beefy serve well and using Petkovic's power to crack some sizzling return winners, although only a smattering of Romans had braved the drops of light rain to see them. She was swinging the racket with gusto at the start of the second set, with a gorgeous net volley and an emphatic smash helping her to hold to love in the second game.
Serena then began attacking the ball too early, leading to unforced errors that let the German off the hook when she was under pressure in the following game. The world number one's rhythm suddenly went astray and she was broken twice on the way to losing the second set, bouncing her racket on the ground in frustration when a netted forehand clinched it for Petkovic. Serena regained her concentration though to win the decider without dropping a game. With an eye on Roland Garros, she said that, despite the problems, her claycourt game was better than at the same stage last season, when she lost here in her first game.