First Open Championship appearance comes at the age of 30 courtesy of an eighth-place finish at the Wells Fargo Championship in May.
Three Royal Liverpool places were up for grabs as part of the Open Qualifying Series, but six of the players ahead of him were or became exempt along with four more alongside him on nine under par, thereby handing the other two spots to himself and Brendon Todd.
Four weeks later McCarthy had a first PGA Tour victory in his sights when he led the Memorial Tournament on the final tee, but bogeyed and then did it again to lose the play-off to Viktor Hovland.
Back in 2010 he played alongside Jordan Spieth and Justin Thomas in the Junior Ryder Cup at Gleneagles and four years later he partnered Bryson DeChambeau and Beau Hossler to victory in the Eisenhower Trophy world amateur team championship in Japan.
He was their top scorer there on 19 under par, but Jon Rahm took individual honours on 23 under. A Walker Cup cap at Royal Lytham & St Annes followed for the same American trio the following season, but Britain and Ireland won that week by a record seven points.
He also made the cut in the US Open before turning professional and it was back at that event last year that he gave his best major performance, a tie for seventh five shots behind winner Matt Fitzpatrick.