However, the 31-year-old, who was playing on an outside court (2) for the first time since 2009 and is still struggling to reach his best form following an elbow problem, managed to continue and clinch the victory.
He has dropped only 12 games in two matches and appeared in top form so appears to be back in with a chance of taking the title, depending on fitness.
He could now face Kyle Edmund in the next round, if the Briton overcomes Bradley Khan.
Meanwhile, Rafa Nadal also won, with a 6-4 6-3 6-4 win over Mikhail Kukushkin.
The two-time champion never quite got to grips with the unorthodox Kazakh's low, skidding shots and faced 13 break points in an entertaining Centre Court contest.
Had Kukushkin converted a few more of them it could have got really complicated for Nadal, who is still finding his grasscourt game after claiming an 11th French Open title.
THe 32-year-old took 10 minutes to hold his opening service game and was still being asked questions by the world number 77 in the third when he slipped 3-1 behind in the face of some inspired shot-making by his opponent.
The 17-times Grand Slam champion dug in though and managed to avoid being dragged further into the afternoon, claiming victory when Kukushkin's forehand smacked into the net tape.
He will face Australian teenager Alex De Minaur in the next round.
No. 2 Rafael Nadal defeats Mikhail Kukushkin 6-4, 6-3, 6-4