MEMPHIS, Tenn. - Bones is back on another bag.

Jim “Bones” Mackay will caddie for FedExCup leader Justin Thomas the next two weeks as Thomas’ regular caddie, Jimmy Johnson, undergoes testing for dizzy spells. Golf Channel’s Chantel McCabe first reported the news.

Mackay, the longtime caddie for Phil Mickelson turned television commentator, will have caddied four of the last five weeks on TOUR. He carried Matthew Fitzpatrick’s bag for the fortnight at Muirfield Village, helping the Englishman finish T27 at the Workday Charity Open and third at the Memorial Tournament presented by Nationwide.

Mackay has carried Thomas’ bag before, at the 2008 Sony Open in Hawaii. Thomas finished T14.

Thomas is a past champion of the next two PGA TOUR events, winning the WGC-FedEx St. Jude Invitational two years ago when the event was still held in Akron, Ohio, and the PGA Championship in 2017.

Memphis also was the site of Mackay’s last tournament with Mickelson. Their quarter-century partnership ended after the 2017 FedEx St. Jude Classic at TPC Southwind. Mickelson finished ninth that week.

Johnson suffered dizzy spells during the third round of the Memorial. Thomas’ father, Mike, carried the bag for the final six holes of the round. Mike Thomas also caddied for his son at the 2018 Sentry Tournament of Champions, which Johnson sat out with a foot injury.

Thomas has a 229-point lead over Webb Simpson in the FedExCup standings after winning twice this season and posting six other top-10s in 13 starts.