Radwanska, the No.3 seed at the Premier Mandatory event, looked headed for a straight set victory after taking the first set and twice going up a break in the second set, for 2-1 and 3-2. Garcia found the range on her big groundstrokes and fought her way back into it, taking the second set, but Radwanska got one last decisive break in the first game of the third set and there were no more breaks from there until Radwanska finally closed out the French qualifier in two hours and 17 minutes, 6-4, 4-6, 6-4.
Radwanska is now tied with Carla Suárez Navarro for most WTA-level match wins on the year - 28.
Garcia certainly left her mark, though. Both players had very positive winners-to-unforced errors differentials, Radwanska +15 and Garcia +13, but Garcia's numbers were much, much bigger, blasting a total of 55 winners in the match, which included 11 aces (Radwanska had 30 winners and five aces).
And it has still been a banner few months for Garcia. Going into Acapulco in February she was on a 10-match losing streak, had never been to a WTA quarterfinal and had never beaten a Top 40 player - since then she has gone 16-5, been to the quarters or better three times (including her first WTA title in Bogotá) and has six Top 40 wins (including Top 10 wins over Jelena Jankovic and Angelique Kerber).
Awaiting Radwanska in the semifinals is No.8 seed Maria Sharapova, who rallied from a set and a break down to beat No.2 seed Li Na earlier in the day, 2-6, 7-6(5), 6-3. Li looked like she was going to cruise to victory after breaking for 4-3 in the second set - she hadn't dropped serve yet in the match - but Sharapova snuck out a break, stayed close with Li for a while, then pulled away at the end.
Sharapova leads Radwanska in their head-to-head, 9-2, which includes 3-0 on clay courts.
The other semifinal will pit No.4 seed Simona Halep against No.5 seed Petra Kvitova. Kvitova was the first to advance, not even having to take the court, actually - Serena Williams, the No.1 seed and two-time defending champion, had to withdraw from the tournament because of a left thigh injury.
"It's beyond words. It's so frustrating," Williams said. "We couldn't ask for a better tournament and I love it here. I love being a champion here. Manolo Santana and his team put on a great tournament.
"This is not the way I wanted this week to end."
"It's sad not to play this match against Serena, but on the other hand I'll have more rest and be more prepared for tomorrow," Kvitova said. ""It can be tough to not play a match, but it depends if you're in the beginning of the tournament or far like this. I'll just practice today and take it as a day off."
Williams is still planning on defending her title in Rome next week, though.
"I am planning to play in Rome," she added. "Fortunately, I have a bye next week so will have an extra day of rest. For now, I will take it one day at a time and take advantage of some extra rest."
Halep advanced with a comprehensive 6-2, 6-2 win over No.11 seed Ana Ivanovic in exactly an hour.
Halep beat Kvitova in their only previous meeting, in the final of New Haven last summer.