Of all the errors Marin Cilic made in another ATP Finals defeat, the most costly one may not have come off his racket.

Cilic made 46 unforced errors as he gave up a break advantage in both sets in losing to Alexander Zverev 7-6 (5), 7-6 (1) on Monday, dropping the Croat’s record at the season-ending tournament to 1-9 across four appearances.

However, the outcome could have been different if Cilic had chosen to challenge when his forehand was called long with Zverev serving at 5-6, 30-30 in the opening set.

Umpire Ali Nili said the call was “close” but Cilic misheard him and video replays showed the ball was in. Having marginally escaped facing a set point, Zverev held serve and took what turned out to be a pivotal tiebreaker.

Alexander Zverev reacts during his match against Croatia's Marin Cilic during the ATP Men's Singles Final, at The O2 Arena in London, Monday Nov. 12, 2018. Cilic made 46 unforced errors as he gave up a break advantage in both sets in losing to Alexander Zverev on Monday. (Adam Davy/PA via AP)
Alexander Zverev reacts during his match against Croatia’s Marin Cilic during the ATP Men’s Singles Final, at The O2 Arena in London, Monday Nov. 12, 2018. Cilic made 46 unforced errors as he gave up a break advantage in both sets in losing to Alexander Zverev on Monday. (Adam Davy/PA via AP)

“I asked him if it was out and he showed me that it was out, clearly, so I didn’t (challenge),” Cilic said. “Even when I hit the shot I felt it was going to be close.”

In the late match, top-ranked Novak Djokovic will begin his campaign for a sixth ATP Finals title against American debutant John Isner.

In a repeat of their opening match last year, Zverev produced the slightly steadier tennis to extend his record against Cilic to 2-0 at the O2 Arena and 6-1 overall.

Alexander Zverev plays a return to Croatia's Marin Cilic during the ATP Men's Singles Final, at The O2 Arena in London, Monday Nov. 12, 2018. Cilic made 46 unforced errors as he gave up a break advantage in both sets in losing to Alexander Zverev on Monday. (Adam Davy/PA via AP)
Alexander Zverev plays a return to Croatia’s Marin Cilic during the ATP Men’s Singles Final, at The O2 Arena in London, Monday Nov. 12, 2018. Cilic made 46 unforced errors as he gave up a break advantage in both sets in losing to Alexander Zverev on Monday. (Adam Davy/PA via AP)

The fifth-seeded Cilic broke at the first opportunity for 2-0 but then wasted break points in the German’s next two service games, before dropping his own serve when attempting to close out the set at 5-3.

“I felt that first part of the match I was much better and he was not into his rhythm,” Cilic said. “I could have won that set comfortably.”

After forcing a tiebreaker with a helping hand from Cilic, Zverev produced one of the points of the match to seal the set as he drew Cilic to the net with a drop shot, then hit a backhand pass up the line.

Croatia's Marin Cilic returns to Alexander Zverev during the ATP Men's Singles Final, at The O2 Arena in London, Monday Nov. 12, 2018. Cilic made 46 unforced errors as he gave up a break advantage in both sets in losing to Alexander Zverev on Monday. (Adam Davy/PA via AP)
Croatia’s Marin Cilic returns to Alexander Zverev during the ATP Men’s Singles Final, at The O2 Arena in London, Monday Nov. 12, 2018. Cilic made 46 unforced errors as he gave up a break advantage in both sets in losing to Alexander Zverev on Monday. (Adam Davy/PA via AP)

Zverev’s mood — and tennis — was much improved in the second, but this time he was the one punished for wasting break points.

Cilic staved off openings at 0-1 and 2-3 before breaking with his first opportunity of the set to take a 4-3 lead, but then made three consecutive wild forehand errors to allow Zverev to break straight back.

The 2014 U.S. Open champion saved a match point at 4-5 with a big serve, but wilted once more as Zverev eased to victory in the second tiebreaker.

Croatia's Marin Cilic celebrates a point during the ATP Men's Singles Final against Alexander Zverev, at The O2 Arena in London, Monday Nov. 12, 2018. Cilic made 46 unforced errors as he gave up a break advantage in both sets in losing to Alexander Zverev on Monday. (Adam Davy/PA via AP)
Croatia’s Marin Cilic celebrates a point during the ATP Men’s Singles Final against Alexander Zverev, at The O2 Arena in London, Monday Nov. 12, 2018. Cilic made 46 unforced errors as he gave up a break advantage in both sets in losing to Alexander Zverev on Monday. (Adam Davy/PA via AP)

“The win, that’s the most important thing,” said Zverev, who failed to advance from the round-robin stage on his debut last year.

___

Source: The Associated Press