Spieth, McIlroy and Day grouped together at Firestone

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Jordan Spieth, Rory McIlroy and Jason Day have been grouped together for the first two rounds of this week's WGC-Bridgestone Invitational, in an eye-catching threesome made all the more fascinating by the US PGA Championship looming on the horizon.

Spieth has the chance to beat McIlroy to the career Grand Slam when the final major of 2017 takes place next week, after the former claimed victory in The Open at Royal Birkdale last month. McIlroy's next opportunity to achieve the feat will come in April at the Masters.

However, McIlroy is likely to fancy his chances in the US PGA at Quail Hollow - a venue where he has enjoyed considerable success - and will get the opportunity to see Spieth close up at Firestone after the groupings and tee times for the Bridgestone Invitational were revealed on Tuesday.

McIlroy - a two-time US PGA champion - is expected to confirm on Wednesday that he has parted company with long-time caddie JP Fitzgerald.

Should this prove the case, McIlroy's replacement on the bag will find himself working alongside two of the most influential caddies in the game. Michael Greller has frequently been hailed for his contribution to Spieth's success, most recently when the Texan triumphed at The Open, while Colin Swatton serves as caddie and coach to Day.

The trio of former world number ones are scheduled to tee off at 8:10am local time on Thursday, starting on the 10th hole.

Immediately behind them will come Dustin Johnson - the man who currently tops the rankings - in the company of U.S. Open winner Brooks Koepka and Hideki Matsuyama.

Masters champion Sergio Garcia has been put alongside Rickie Fowler and Matt Kuchar in a group starting from the first at 9:20am on Thursday.