Rory McIlroy appears determined to hold on to his world number one ranking at all costs after he blasted his way back up the leaderboard in last night's second round of the WM Phoenix Open.

Defending champion Scottie Scheffler, the world number two, and third-ranked Jon Rahm can return to world number one at McIlroy’s expense this week.

And both took advantage of McIlroy shooting a two-over 73 in round one to hit the front at TPC Scottsdale.

Scheffler, who can return to number one with a win if McIlroy finishes worse than third alone, followed an opening 68 with a seven-under 64 to set the clubhouse target at 10-under at halfway.

But he leads by just two strokes from Rahm, who followed an opening 68 with a 66 to share second place with Adam Hadwin (10 holes) as he looks to finish second alone at worst and hopes McIlroy finishes worse than 47th alone and Scheffler doesn't win.

McIlroy was tied for 69th after his two-over 73 in round one, but he ended the day tied for 18th n three-under, just five strokes behind Scheffler, after ripping off five birdies in 13 holes before darkness fell.

The Holywood star (33) insisted this week that he feel likes the best player in the world and hopes to double his tally of wordwide wins before he’s done.

Having said his first round was “just one of those days”, normal service appear to be renewed when he birdied the second from seven feet, missed a six-footer for eagle at the third, then rolled in a slick 25-footer from the fringe at the par-three fourth to move into red figures.

He then hit a wedge to eight feet at the fifth and made the putt to go four-under for the day and parred the next five holes before making a 14-footer for a two at the 203-yard 12th.

He ended the day tied for 18th on three-under— five-under for the day— with five holes of his second round to complete today.

Seamus Power is tied for 49th on level par after back-to-back 71s, but Shane Lowry needs a hot finish to avoid missing his second cut in a row this year.

After opening with a 75, the former Open winner made two birdies and two bogeys on the back nine at TPC Scottsdale before three front-nine pars left him four over with six holes to complete today.

With the cut projected to fall at one over par, Lowry likely needs three birdies in his last six holes to avoid another weekend off.

He split with long-time caddie Brian "Bo" Martin following his missed cut in the Dubai Desert Classic and has just started working with Bray's Darren Reynolds this week.

As for the battle for world number one, Masters champion Scheffler insisted that being considered the world's third-best player behind Rahm and McIlroy is not something that's keeping him awake at night.

"Not really," he said. "I would probably have to agree. It's not like I'm sitting there saying I'm playing better than those guys right now. They have been winning tournaments and I've been kind of on the outside looking in. So no, I haven't really been paying attention to it too much."

As for a potential showdown with Rahm for the world number one spot this weekend, he knows there are other players in the mix.

"Yeah, I mean that would be a lot of fun," Scheffler said. "It looks like right now we're 1 and 2, but we'll see how things shake out. A lot of guys still have a lot of golf out there to play. Should be a fun weekend."

Rahm has won five of his last seven events compared to three wins for McIlroy in the same span.

But the big Basque is not getting too caught up worrying about who is considered better right now.

"Listen, you can find a criteria or algorithm that's going to make me No. 1 at any given point," said Rahm, who is ranked number one by the DataGolf system.

"I feel like I've been No. 1 and I wasn't playing as good as I am right now. So it doesn't really matter. You got to keep doing it.

"Yes, I've been playing great golf. But Rory has also won three of his last eight starts (sic), so it makes sense that he stays up there. Scottie did enough last year to stay up there. He's been playing great. He hasn't won, but he's been up there. That still racks up points.

"So I feel like I'm playing great. I feel like, again, if I'm not the best, I'm one of the best. Just because I have been playing good and I'm confident on myself. But I don't get too much in that discussion. A lot of what we say about the ranking is more for fun than anything else."