Samantha Stosur admitted on Thursday's quarter-final win over second-seed Vera Zvonareva, her best of the year so far as she reached the last four at Stuttgart's WTA tournament.
The 27-year-old Australian fifth-seed battled back from losing the first set for a 2-6, 6-3, 7-6 (7/3) victory over the Russian, who is ranked third in the world, in just over two-and-a-half hours.
Having made an early exit from January's Australian Open, Stosur is hoping to use Stuttgart to recapture the form which helped her reach the French Open final at Roland Garros last year.
"That's probably the best match I have played all year," beamed Stosur after reaching the last four of a tournament for the first time in 2011.
"It is very encouraging to beat a player as good as her in a tough, tight match."
Zvonareva repeatedly broke her racquet strings and even played parts of the match with her coach's racquet.
After the Russian had dominated the first set, the match turned in the second when the 26-year-old needed lengthy treatment for a problem with her right shoulder with the score at 2-1 to the Russian.
Stosur capitalised with a series of strong serves to take a 5-3 lead when she then broke the Russian to take the third set.
There was drama in the third with the scores locked at 5-5 as both players broke the other to set up the tie-break.
Stosur raced into a 5-0 lead before Zvonareva rallied briefly, but the Australian hung on to go into the semi-finals where she will face either her German doubles partner Sabine Lisicki or Germany's Julia Goerges.
"I am not surprised the Germans are doing so well here," said Stosur.
"They have good players and a lot of support here after their Fed Cup win.
"I have been playing with Sabine this week, so I know what a good player she is."