The Open: Phil Mickelson still a force, says former caddie Jim 'Bones' Mackay

Mackay said Mickelson's 2013 Open victory was the best of their time together

Phil Mickelson is being tipped for more major success by his long-time former caddie Jim 'Bones' Mackay, who insists the 51-year-old veteran is a live contender at next week's Open at Royal St George's.

Mackay, who was on Mickelson's bag for five of the left hander's six major titles, made his comments in a wide-ranging interview with BBC Sport.

He believes his former boss played his best ever golf when he won the 2013 Open at Muirfield.

He also thinks former US Open champion Bryson DeChambeau should try to reconcile with estranged bagman Tim Tucker.

And on the Ryder Cup Mackay conceded that victory does "really matter", despite Jack Nicklaus stating the contrary following the launch, this week, of a new sportsmanship award at the biennial match between Europe and the US.

Mackay will be part of the on-course commentary team for NBC at next week's Open at Sandwich. The last time he was at the Kent course he was helping Mickelson finish runner-up to Darren Clarke in 2011.

Two years later, his then boss surged to victory at Muirfield for one of the biggest moments of his illustrious career.

"It might have been the most massive to be quite honest with you," Mackay said.

"That Sunday at Muirfield in 2013 is probably my favourite day, for a number of reasons, that I ever had as a caddie.

"His warm up was so good, I remember him turning around and saying to Butch (Harmon) and I 'my goodness I'm hitting every shot exactly where I'm looking, should I keep on going or should I take a minute off here?'

"To come from five back as he did and win by three and have players walk up to you after the day ended and say 'my goodness what course were you playing?' It was the best round of golf I ever saw him play, period.

"And it was on an incredibly big stage and at an incredibly important event and that, for me, just means the world."

Mickelson heads to Sandwich as the reigning US PGA Champion after becoming the oldest major winner at Kiawah Island in May.

"I really don't care what he's done in the weeks since the PGA, he knows he can do it, that's the bottom line," Mackay said.

"He'll have a good feeling about the way that he played at Royal St George's the last time he was there.

"The guy just never got enough credit for certain things that he does. He's incredibly proficient at flighting his irons and certainly you won't win an Open Championship if you can't play in the wind."

The 56-year-old Mackay also credits the enduring efficiency of Mickelson's short game. "I always said that Phil would win a major in his 50s," he said.

"I was wrong when I assumed it would be the Masters. He's certainly proven to me that he's going to be a force for several years going forward."

Mickelson and Mackay were one of the mainstays of the American Ryder Cup team for more than 20 years

This September Mickelson could continue his run of playing every Ryder Cup since 1995. A new accolade for sportsmanship in the match, the Nicklaus-Jacklin Award, presented by Aon, was announced this week.

Nicklaus, winner of a record 18 majors, stated on social media that he believes the occasion to be "a goodwill match between golfing nations", adding "I don't think who wins is all that important".

Mackay, an Aon brand ambassador, who caddied for Mickelson in every Ryder Cup between 1995 and 2016, does not see it the same way.

"Absolutely it does matter who wins," he said. "It's just incredibly intense and it means so much to everybody.

"I remember the last time the US won in 2016, just looking over at Rory (McIlroy) and you could see just how upset he was."

But Mackay knows better than most that there is room for acts of sportsmanship in the heat of Ryder Cup battle. In 2012 he was at Mickelson's side when Justin Rose holed a crucial long range putt on the 17th hole of their singles contest.

It sensationally helped Europe complete their "miracle at Medinah" comeback. "In matchplay they say expect your opponent to hole everything," Mackay said.

"But in my 30 odd years out there on the tour, that putt - in particular - probably surprised me as much as any putt I ever saw made."

As Rose celebrated, Mickelson sportingly applauded. "It was an absolute shock and yes for Phil to take it like he did was incredibly impressive.

"Relative to the sportsmanship that Aon is looking to honour with this award, Phil would have certainly been a worthy candidate that afternoon."

Having given up full-time caddying, Mackay is an interested observer following the surprise break up between 2020 US Open champion DeChambeau and Tucker, his long-time bagman, last week.

Mackay says DeChambeau is choosing from a reduced selection of potential replacements because of his unorthodox approach to the game.

"Bryson is one of the best players in the world and it is quite possible that Tim is as good a caddie as he could possibly find," said Mackay.

"For the vast majority of players there's a large number of caddies who could work for that player and do a very, very good job.

"Because Bryson is a little bit different in terms of what he wants and how he wants it, I think that pool of guys he could successfully pick from is quite a bit smaller.

"So if I was Bryson, I would make sure that I'd done everything I could, if he wanted Tim to come back at some point."

Mackay highlighted the relationship between Bubba Watson, another unorthodox character, and his caddie Ted Scott. "They have this amazing brotherly relationship that will go on as long as Bubba chooses to tee it up," he said.

"It is important for Bryson and I'm sure he's thought about it a lot in the last couple of weeks."

McKay added: "It's up to both of those guys to sit down, have a conversation, figure out what they both want and if, indeed, there is a chance that they both think they can get back together.

"I hope they do because they're very good for each other."

With the 149th Open fast approaching, Mackay has swapped golf bag for microphone aware that his former colleagues face one of their most demanding weeks.

"You have to know the golf course so incredibly well," he said. "It was probably the only golf tournament that I went to as a caddie that I would walk two or three times prior to seeing it with my player on the Thursday.

"You never can quite know enough about those golf courses."

And he cannot wait to return to the first running of the championship for two years and the galleries who will be watching. "I'm looking forward to 32,000 people a day," Mackay smiled.

"Golf's not complete without the Open Championship being played, it's incredibly important and I just can't wait to see it with my own eyes."