A decision not to fill the fifth roster spot with doubles standout Rajeev Ram backfired in more ways than one against Italy Thursday.

The Canadians will next take on Italy, who surprised the United States in the other quarterfinal tie of the day.

U.S. captain Mardy Fish's roster includes No. 9-ranked Fritz, who is coming off a run to the semifinals at the ATP Finals, and No. 19 Tiafoe, along with doubles specialist Jack Sock and Tommy Paul.

The Serbian found a way to make it to the finish line first—by a nose—in each set during Saturday's 7-6 (5), 7-6 (6) success.

The 21-time major champion will play for a record-tying sixth title at the ATP's year-end event after advancing, 7-6 (5), 7-6 (6), Saturday in Turin.

One player has dominated the other in each of these match-ups, but there are reasons to favor the underdogs.

The American, who saved all three break points he faced in a standout service performance, will take on Novak Djokovic next at the ATP Finals.

Fritz battled past Felix Auger-Aliassime, 7-6 (4), 6-7 (5), 6-2, to become the first American to reach the final four at the season finale since Jack Sock five years ago.

With the winner advancing to the semifinals, we're banking on this one being quite competitive.

With the Norwegian already through to the semifinals, will FAA or Fritz join him come Thursday in Turin?