Patrick Cantlay's caddie Joe LaCava apologised to Rory McIlroy before Sunday's Ryder Cup singles for his behaviour on Saturday which enraged the European star, according to US media reports.
McIlroy was livid after LaCava continued to celebrate a brilliant putt by Cantlay on the 18th green near the Northern Irishman while he was preparing for his own effort to tie their fourballs match.
American media said LaCava requested to meet McIlroy on Sunday morning to apologise and clear the air.
Cantlay and LaCava were met with deafening boos on the first tee in Rome when they arrived for the world No 5's match against Justin Rose.
The American had also brushed off media reports that he was protesting against the lack of pay for players at the Ryder Cup by not wearing a cap.
The home crowd waved their hats at him from the opening tee box and all the way down the first fairway.