An out-of-sorts Novak Djokovic fended off an inspired Gilles Simon to mark his return to the ATP Tour with a battling 6-3 3-6 7-5 victory at the Monte Carlo Masters.
The world number two has struggled with form and injuries so far in 2017 and missed the Miami Open with an elbow problem, although he did represent Serbia at the Davis Cup this month.
Djokovic, playing his first match on clay this season as he builds towards defending the French Open, coasted through the opening set and, after breaking early in the second, looked on course for a straightforward second-round win.
But as his level dropped, Simon's improved dramatically and some inspired tennis saw the Frenchman roar back to restore parity.
Simon twice led by a break in a back-and-forth decider, only to hand the advantage back to Djokovic - who hit an uncharacteristic 43 unforced errors - and he made the most of his reprieve to come through a match he will hope can kick-start a flagging season.
Djokovic was superb in a dominant opening set in which some big-hitting and solid defence saw him take the lead.
It appeared as though the writing was on the wall when Djokovic broke early in the second set, but Simon's aggressive play left his opponent chasing shadows and yielded four straight games en route to levelling the match.
A stunning low volley and a deft lob brought up a break for Simon in the decider, but Djokovic displayed his battling ability to level at 3-3, before he again had to dig deep when Simon broke for a 5-4 lead thanks to the Serbian finding the net with his opponent's right wing gaping.
This time Djokovic - knocked out at this stage by Jiri Vesely last year - hit back and then held for 6-5 and, with the pressure on, Simon's luck was out as a broken string on match point saw him skew wide.
Djokovic  bt Simon 6-3 3-6 7-5
Djokovic - 23/43
Simon - 21/26
Djokovic - 2
Simon - 0
BREAK POINTS WON
Djokovic - 6/16
Simon - 5/6
FIRST SERVE PERCENTAGE
Djokovic - 61
Simon - 56
PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Djokovic - 63/59
Simon - 60/49
Djokovic - 93
Simon - 83