Padraig Harrington believes Rory McIlroy will win the Masters "when we least expect it" but admits that he now faces a big challenge with Jon Rahm clearly "the man" to beat in world golf.

Speaking at the opening of the Marlay Putting Green — funded by the Padraig Harrington Charitable Foundation, a golf development grant from the R&A, and a grant from Golf Ireland — Harrington admitted McIlroy is no longer the alpha dog who won four Majors in three years and faces a big pack of rivals with Masters champion Rahm the new kid on the block.

"It's a mental challenge for us all and no more so than for Rory," Harrington said. "We know he has the physical ability and that's a burden at this stage in some ways because everybody's expectation is so high because he physically could win at any moment.

"I think clearly trying to win the Masters is a tough one and maybe winning another major could be the way forward for him to get back on that winning way in Majors and then the Masters falls into place. The great thing for Rory is he could win one any time. It could happen tomorrow.

"As much as people get frustrated he didn't win the Masters, or didn't win the last Major, he still has the game that when he turns up and it falls into place, he can win any given week.

"But there are new kids on the block and that makes it hard.

"Jon Rahm is turning up at every event and he is walking out there fully believing nobody can beat him.

"That's the Rory of 2013 walking out there and believing nobody can beat him. Jon Rahm is that man now. DJ was that man. Jordan Spieth was that man. Brooks Koepka was that man.

"So it does move on. But Rory still has enough game where if he turns up and it's his week, he could definitely win any tournament."

Harrington felt McIlroy was the clear favourite for the green jacket after looking impressive in his run to the semi-finals of the WGC Dell Technologies Match Play in Texas in his final warm-up event.

But he reckons the weight of expectation on his shoulders, coupled with competition from the likes of Rahm, makes it difficult to win on command.

"I don't think it is scar tissue or experience," Harrington said. "I just think there is a lot of hype going into it. A lot of pressure. He has tried a few different ways of going about it, and I think he will win it when we least expect.

"He was so hyped up after playing well at the Match Play, with hindsight, I think he will probably win it when we least expect it. When we have all got our backs turned, he will come out and win it.

"I think winning another Major might be a nice way of dissipating some of that extra pressure."

Harrington won three majors in 13 months between 2007 and 2008 but no tournaments at all when he played his best golf in 2009 and 2010 until he claimed a small Asian Tour event at the end of 2010.

"Sometimes going in without as much expectation could be a good thing," Harrington added. "But that is not often for Rory because there are so many people that are rooting for him.

"After his Match Play performance, even I put him as the favourite going into the Masters. Everything looked good. Driving and putting looked really good. I thought he was going to be up there.

"Jon Rahm hadn't been so good the previous couple of weeks, but Jon Rahm at the moment just believes he is the best player. It's a nice place to be."

As for the new putting green, where putters and balls are available free to the public, Harrington was thrilled to see it finally open.

"Three years ago, we had this idea that we would build a putting green," he said. "It's immensely easy for people to do and it is very satisfying, for beginners particularly. And yet, as we know, when you become an accomplished golfer it's actually the hardest thing to do.

"So I wanted to build something that beginners would come along and not be afraid of, have a bit of fun, no rules or regulations in the sense that you could come on here in your jogging gear and your t-shirt and shorts. Anything you really like. The only thing we're stopping is football boots or something like that.

"So somewhere you can have a bit of fun and don't get too stressed. And hopefully people will enjoy it. And maybe if people enjoy it, they might say, 'you know what, we might try the par-3 course,' which is only a hundred yards away. And if they like that, they might advance to golf, so it is just to introduce people in a less pressurised, fun environment."