Angelique Kerber put in a Jekyll and Hyde performance but eventually defeated Mirjana Lucic-Baroni 6-2 7-6 (9-7) in the second round of the US Open on Wednesday.
The second seed appeared on course for a dominant victory on Louis Armstrong Stadium having outplayed her opponent to move into a 6-2 4-1 lead in hot New York conditions.
However, the Australian Open champion suffered an uncharacteristic slump to allow Lucic-Baroni - whose own erratic performance was highlighted by 37 winners and 55 unforced errors - back into the match and the Croat even had two set points to force a decider.
Kerber regained her composure, though, and the German - whose sublime 2016 has included runner-up finishes at Wimbledon and Rio 2016 - booked her place in round three in a time of one hour, 34 minutes.
Kerber's powerful groundstrokes and dominance at the baseline soon had Lucic-Baroni on the ropes and in no time the Olympic Games silver medallist had raced into a 4-0 lead.
Lucic-Baroni finally settled in the contest and she put herself on the scoreboard in game five, but 24 first-set unforced errors gifted Kerber too many easy points and the opening set was clinched with a big ace.
The second set started in a similar fashion as Kerber's ability to mix up her game left Lucic-Baroni toiling and she soon had a 4-1 double-break lead.
But surprisingly Kerber's service game deserted her while Lucic-Baroni shifted through the gears to reel off four consecutive games and move ahead in the set.
The set headed into a back-and-forth tie-break and Lucic-Baroni twice had the chance to force a decider, but it was not to be as Kerber's resilience shone through and a long forehand from the former on match point brought an end to proceedings.
Kerber  bt Lucic-Baroni 6-2 7-6 (9-7)
Kerber - 11/15
Kerber - 2
Lucic-Baroni - 4
BREAK POINTS WON
Kerber - 5/9
Lucic-Baroni - 3/6
FIRST SERVE PERCENTAGE
Kerber - 57
Lucic-Baroni - 46
PERCENTAGE POINTS WON ON FIRST/SECOND SERVE
Kerber - 68/50
Lucic-Baroni - 59/43
Kerber - 84
Lucic-Baroni - 71