Patty Schnyder spoke of retirement after losing in the first round of the Australian Open last month but responded by upsetting the seedings in the Dubai Open on Tuesday.
Schnyder's 4-6, 7-6 (7/2) 6-2 win over former world number one Ana Ivanovic was her first of a year which has been blighted by bronchitis and other health problems.
Now the 32-year-old was a canny revelation. She recovered from a set and 1-3 down with loopy left-handed forehand drives and changes of pace, which together began to gnaw at the 14th-seeded Ivanovic's confidence.
"It feels great to win, especially after what I've been through," said the former world number seven from Switzerland.
"She was taking the ball early and hitting it hard. I started to find my footwork a bit. I was kind of slow, but I hung in there."
Schnyder was also the more consistent player. She gained the first mini-break in the tie-break by inducing the dangerous but inconsistent Ivanovic to pull a forehand wide, and then attacked a moderate second serve to go two mini-breaks up.
Ivanovic responded with a lengthy argument about a line decision with the umpire, while some of the crowd bellowed "out".
The official appeared to refuse to call for the Hawkeye replay system because Ivanovic continued a rally before deciding to make her appeal. Replays suggested in any case that Schnyder's deep return had hit the line.
After Schnyder went on to take the tie-break 7-2 she gained increasing momentum, breaking serve immediately in the third set and recovering from 15-40 down in the sixth game to reach 4-2.
The match was effectively over when Ivanovic served two successive double faults to concede another break, another indication of fragile self-belief.
It was a particularly disappointing setback for the talented and glamorous but enigmatic Serb, who has just parted with Antonio van Grichen and decided to tour without a coach.
Schnyder will now play Zheng Jie, the former Wimbledon semi-finalist from China, who needed three sets to get past Kristina Barrois, a German qualifier.
Zheng was joined in the second round by compatriot Peng Shuai, who followed two wins in the qualifying competition with a 6-2, 3-6, 6-3 success against Bethanie Mattek-Sands, a former United States Fed Cup player.
Another seed to depart was the 13th rated Petra Kvitova, who won the Paris Open by beating the US and Australian Open champion Kim Clijsters on Sunday.
The Czech now lost two tie-break sets to Ayumi Morita, a Japanese qualifier, and was joined at the exit by another jaded-looking champion from two days previously.
That was Daniela Hantuchova, who won the Pattaya Open but had little energy left with which to trouble Anna Chakevetadze in a meeting between two former top ten players.
The Russian trampled through 6-1, 6-3 to earn a meeting with top-seeded Caroline Wozniacki, who could regain the world number one ranking from Clijsters this week.