ROME, Italy - A heavyweight clash of former World No.1s in the Internazionali BNL d'Italia quarterfinals saw No.9 seed Garbiñe Muguruza move into the last four at the Foro Italico for the third time with an absorbing 3-6, 6-3, 6-4 defeat of Victoria Azarenka over two hours and 19 minutes.

The result marks Muguruza's belated revenge for the pair's only previous completed match, a superb 7-6(6), 7-6(4) win for Azarenka in the fourth round of Miami 2016.

Each of their meetings since then - both in 2019, one in the third round of this very tournament - had ended in retirement, but the sense of unfulfilled promise around their rivalry was significantly dispelled by the nature of today's contest, noteworthy not only for the quality of the players' ballstriking but for their tactical adjustments throughout.

This was particularly evident in a magnificent final frame, in which Muguruza led 3-1 but had to fight off a point to fall behind 3-5.

"I think it was a tough match. I knew it was going to be a tough match. She's a good player, she's playing good, she's with a lot of confidence," Muguruza assessed.

"I knew it was going to be a tough battle. I was ready for it. I stood behind her and waiting for my opportunities. She was playing great at the beginning. She took the first set. I kept myself together and said, 'Okay, let's start another battle in the second set.'"

The key sequence of the first set was the stretch of three games following an initial service hold for both players. Each of those featured at least one break point as the two-time Grand Slam champions engaged in a series of high-octane baseline rallies, attempting to force errors from the other with depth and placement - and it was Azarenka who was able to better take her chances.
Muguruza held two break points to go up 2-1, but missed both due to errant forehands, with Azarenka eventually holding thanks to a phenomenal volley pickup.

The Spaniard's groundstrokes continued to go awry in the next game, with Azarenka taking her first break point opportunity as a Muguruza backhand went long. Adding to her woes, the Australian Open finalist was then unable to convert triple break-back point, Azarenka finding strong serves when she needed them to reel off five points in a row for a 4-1 lead.

There would be no further chances for either in the opening act; Muguruza was able to keep the deficit to one break, but could not prevent Azarenka eventually serving the set out with little fuss, finding a smash and service winner on the last two points.

In contrast to an opening act where the serve had largely reigned supreme, the second set would be a patchier, tenser affair that featured seven breaks of serve in nine games. Initially, Muguruza still seemed to be at sea after losing the first set, coughing up a double fault, a plethora of errors and an erroneous challenge to twice go down a break.

But the World No.17 was beginning to find her range on return - and to take advantage of the sprinkling of double faults that had hitherto been the only vulnerability in Azarenka's game. Finding a series of authoritative forehand winners, Muguruza broke back immediately both times - and then delivered the set's only convincing hold to move up 3-2.

Having finally wrested some momentum from Azarenka, the 2016 Roland Garros champion found it difficult to maintain: despite continuing to have her way with her opponent's delivery, Muguruza dropped her own to love again in the seventh game, finishing with her third double fault. As the 26-year-old served for the set, Azarenka would threaten another resurgence as the quality suddenly rose several notches: the US Open finalist saved a first set point with a phenomenal forehand pass on the run, and three times made her way to break-back point.

Muguruza would need to summon all of her intensity to close out the game, finally sealing it after four deuces with a service winner on her second set point. Crucial to this passage of play had been the 2017 Wimbledon champion's efforts to move up the court - a risky strategy given the quality of Azarenka's passing shots and lobs, but one that also set up several straightforward overhead putaways for Muguruza.

The deciding set opened with much the same pattern as the second: an initial sequence of exchanged breaks, broken when Muguruza began to pull away, nailing a backhand winner down the line for a 3-1 lead.

By now, both players were playing some of their best tennis of the day, making for a number of riveting baseline battles. But arguably the best of these - Muguruza showcasing superlative defence before nailing a forehand winner down the line the moment she saw the opening in the sixth game - in fact triggered a momentum shift away from the two-time Rome semifinalist. Azarenka had already raised her own level, having snapped a six-break streak against her serve in the fifth game, and followed that up with another two games to take a 4-3 lead over a suddenly error-strewn Muguruza, whose forehand accuracy had suddenly disappeared.

With the resurgent two-time Australian Open champion six points away from victory at 0-30 on the Muguruza serve, and then five points away when she held a break point to go up 5-3, Muguruza was forced to snap out of her funk quickly. To the rescue came her trusty backhand, which delivered a winner to save that break point, and a pair of service winners to escape from the game.

This week, Azarenka's stamina and rapid adjustment to the Roman conditions after her run over the previous three weeks to the Cincinnati title and US Open final have been remarkable. But holding that point for 5-3 would be the Belarusian's limit: Muguruza would run off the next 10 points in a row to essay a final momentum shift, relentlessly breaking down Azarenka's forehand to advance to triple match point.

"I was in the right place when the opportunity came and I took it," the Spaniard said. "At the end of third set, it was just a matter of one-game difference.

"I'm happy I played the right shots and I stood aggressive. I went for the match the whole time. Never felt down. I went for the match."

An Azarenka backhand found the net on the third of those, sending Muguruza through to a semifinal date against No.1 seed Simona Halep - where she will seek to reach the Rome final for the first time, having fallen in the last four in 2016 to Madison Keys and in 2017 to Elina Svitolina (via retirement).

"It's a semifinal. It's what I expect these type of players to face," Muguruza said. "It's always a battle, again. She's playing good. She's a good clay court player. Every surface, but a good clay court player, as well.

"I'm just looking forward to another battle, because from now on, every match is a battle. Especially now you're facing one of the best players. I'm excited. I'm excited to be part of this."

2020 Rome highlights: Muguruza fights back to beat Azarenka