AKRON • Playing in each other's company at the Bridgestone Invitational in Akron, Ohio, Jordan Spieth and Rory McIlroy seemed as happy as sandboys; on holiday, the stresses of the British Open left far behind.

This week, it will be back to the serious business of trying to win Major championships as the fourth and final one of the year, the PGA Championship, unfolds at Quail Hollow, North Carolina.

Quite rightly, they are joint favourites, for Spieth is the man of the moment as Open champion, and McIlroy has an unmatched record at Quail Hollow, with two wins and the course record.

This week and beyond, the consensus is growing that, although others will no doubt intrude from time to time on their private party, these two will contest supremacy.

In the Bridgestone tournament - which ended this morning (Singapore time) and where Belgium's Thomas Pieters (66) and two-time Major winner Zach Johnson (65) held the lead after the third round on 201, one stroke in front of Australian Scott Hend, who carded a sensational 63 on Saturday - Spieth and McIlroy have been playing as if for recreation, with smiles on their faces and delight, perhaps a little envy, in each other's talents.

Each had arrived in Ohio with a considerable weight lifted off his shoulders. McIlroy, who carded a 68 on Saturday to head a group on 204, had sacked his caddie, J.P. Fitzgerald, his faithful bag carrier since July 2008.

Spieth, who had a third-round 71 for a 208 total at the Bridgestone Invitational, had already proved that he could close out a Major in the most demanding circumstances, laying to rest the meltdown he had suffered at the Masters last year.

Both could dwell on the matter of caddies. Spieth has a great one; it is clear that McIlroy needs one.

After his stunning victory at Birkdale, Spieth paid tribute to his caddie, Michael Greller. He had made three vital interventions to help the Texan climb out of a deep hole and win the tournament.

"You deserve all the credit in the world for this Major championship," Spieth said to Greller as he cradled the Claret Jug.

Greller, a former maths teacher, has been Spieth's caddie since the American turned professional in 2012. In that time, he has learnt his trade and above all learnt when to intervene with his player, and when to keep quiet.

McIlroy now has a close friend, Harry Diamond, to carry his bag. Diamond is a good companion and an excellent player himself, but has little experience as a caddie.

That has not mattered so far. As McIlroy said: "We both did the numbers and I sort of consulted him a couple of times. It was good."

But he needs a long-term caddie who knows his craft, whose company he enjoys and who can learn McIlroy's game and personality to know when to let him freewheel and when to apply the brakes.

Then McIlroy can fully apply himself to the task of beating all the others, and especially Spieth, his good friend and most dangerous rival, and the man who will beat him to the career Grand Slam if he wins at Quail Hollow.

THE TIMES, LONDON, AGENCE FRANCE-PRESSE