Westwood, who has led 48 of the 49 holes he has played this week, got a small measure of revenge against Nick Watney and advanced to the quarterfinals with a 3-and-2 victory on Friday at Dove Mountain. Watney had eliminated him each of the last two years.
Westwood or McIlroy would go to No. 1 in the world with the title in this World Golf Championship. If they win their quarterfinal matches Saturday, they would meet in the semifinals Sunday morning.
"It's a nice incentive," McIlroy said. "It's nice to have in the back of your mind. And if you're struggling in a match and find it hard to get yourself up, or get any sort of momentum, if you think about that and you think if you can really dig deep, you still have a chance to become No. 1."
Westwood was at No. 1 a year ago, and it's a less of a priority than to capture his first World Golf Championship.
One year after Luke Donald became the first Match Play champion to never trail all week — Donald never even played the 18th hole in his six matches — Westwood is look every bit as dominant.
He is equipped with an improved short game, and it has carried him along the high desert. Westwood put away Watney for good with a pitch up a steep slope to the top tier on the 15th green, the ball so close that Watney picked it up for him.
Westwood had never made it out of the second round in 11 previous trips to this fickle tournament.
"I'm just happy to be looking for a different restaurant for Friday night," Westwood said. "I had a little chuckle watching The Golf Channel on Wednesday morning and listening to them make all their predictions and things like that. I don't think they got many right."
And where did the prognosticators have Westwood?
"On the BA 289 on Thursday night," he said, referring to his usual British Airways flight.
Next up for McIlroy is Bae Sang-moon of South Korea, the surprise in his first Match Play Championship. Bae won three times last year on the Japan Golf Tour. And while he made it through Q-school to earn a PGA Tour card, he ended last year at No. 30 in the world.
He is no stranger in global golf, as McIlroy knows all too well.
They played in the final group of the Korea Open in 2009, where McIlroy and Kim Dae-sub were tied for the 54-hole lead. Bae closed with a 67 and beat them both.
Bae had the only match that went 18 holes in one of the dullest third rounds ever at the Match Play Championship. He took a 1-up lead on the 16th hole against John Senden when the Australian played a poor chip. Senden missed a 20-foot birdie putt to square the match on the 18th, and Bae completed a long two-putt par with a 5-footer.
"He's been very impressive this week," McIlroy said.
In other matches:
— Hunter Mahan took advantage of some mental lapses by Steve Stricker to build a big lead and held on for a 4-and-3 win. Mahan will play Matt Kuchar, a 4-and-3 winner against Martin Kaymer, a finalist last year at Dove Mountain. That assures there will be an American in the semifinals at the Match Play for the first time since 2009.
— One year after Mark Wilson was drubbed in the second round by big-hitting Bubba Watson, he overwhelmed another power player by beating Dustin Johnson for the second straight year. Johnson was too wild too often and couldn't make putts, a bad combination in match play. Wilson will play Peter Hanson of Sweden, who dismantled Brandt Snedeker during a quiet, effective march to the quarterfinals.
"I know people keep talking about how I hit it so short that I can't compete," said Wilson, who has won three times on the PGA Tour in the last 14 months. "First of all, I don't hit it very short. And secondly, it all comes down to putting. It really does. So I just don't know how many times I have to explain it."
Watney eliminated Tiger Woods on the 18th hole Thursday, despite a poor round of putting. His stroke didn't get much better, and that left him little chance against Westwood.
Watney's only hope for a shift in momentum came on the par-5 13th, when he was 10 feet away for birdie. Westwood was just short of the green in two, and his pitch hit the flag and caromed about 12 feet away. The Englishman holed his birdie putt to stay 3 up, and they halved holes the rest of the way.
"I couldn't sit at his lunch table," Watney said, poking fun at Kobe Bryant's comment about the Oklahoma City Thunder.
Stricker holed a 20-foot birdie on the fifth hole that looked as if it would square the match until Mahan matched him with a birdie from 15 feet just off the green. Two holes later, Mahan took the lead. Stricker hit a driver into the desert on the 10th to lose the hole, then pulled his 3-wood into the desert on the next hole.
Stricker knew he was doomed on the par-3 12th, when he watched Mahan roll in a 55-foot birdie putt with perfect pace. Stricker stood off the green and smiled, walked over to retrieve the ball from the cup and started to hand it to Mahan. Then he stopped, and heaved the ball into the grandstand as Mahan laughed.