Watch Justin Thomas challenge Jordan Spieth's caddie to a tricky two-putt at the Open Championship

The practice rounds are underway from Carnoustie Golf Links for the 2018 Open Championship. While there was plenty of fun to be had by the players preparing for the third major of the season, Jordan Spieth's caddie Michael Greller was all smiles, one-upping 2017 PGA Championship winner Justin Thomas.

The Open Championship tee times, pairings | Practice round photos

Greller, who had caddied for Thomas before, stood at the 18th hole alongside Spieth. Thomas challenged his former caddie from roughly 70-feet away, daring him to sink a two-putt with a wedge. When Greller came up about 15 feet short on his first putt, Thomas was joyfully celebrating, but it was Greller who had the last laugh, sinking the two-putt and answering the call.

The Open Championship kicks off Thursday morning from Angus, Scottland. While Greller will man the bag for Spieth on his quest for a repeat title, Thomas will be looking for some memorable putts of his own over the weekend.