Novak Djokovic had to dig deep into his extensive reserves to see off a brilliant Gilles Simon at the Monte Carlo Masters, but Jo-Wilfried Tsonga had no such luck.

Four of the 15 singles matches at the ATP 1000 event were second-round contests, the highlight of which was undoubtedly Djokovic's encounter against Simon as the Serbian fought to a 6-3 3-6 7-5 win.

However, it was a different story for Tsonga who was shocked by French compatriot and qualifier Adrian Mannarino despite winning the first set on the Monte Carlo clay, the seventh seed going out 6-7 (3-7) 6-2 6-3.

DJOKOVIC UNCONVINCING ON RETURN

Djokovic has been hampered by poor form and injuries in 2017 and missed the Miami Masters with an elbow complaint, although he did play in the Davis Cup this month.

Initially, the Serbian looked in fine fettle as he cruised through the opening set, but the former world number one had no answer to an inspirational Simon in the second.

Twice Simon led by a break in the decider, but ultimately Djokovic displayed his trademark battling qualities to fight back and continue his quest for a third title in Monte Carlo.

MAGIC MANNARINO SENDS TSONGA TUMBLING

Mannarino had already won two qualifying matches and beaten Guillermo Garcia-Lopez in round one, but there were no signs of fatigue as his stinging backhand helped improve his record over top-10 players to 2-18.

Tsonga, a two-time semi-finalist in the principality, had fought back from 3-1 down in the decider, but Mannarino would not be denied.

"I never expected to beat Jo. I certainly didn't expect to beat him on clay. But I tried not to think he was on the other side of the net. I just focused on what I had to do," he said.

GOFFIN AND CUEVAS IN CONTROL

Only two other seeds were in second-round action with David Goffin (10) and Pablo Cuevas (16) seeing off Nicolas Almagro and Joao Sousa in straight sets.

Lucas Pouille (11) was too good for American Ryan Harrison in a 6-2 6-4 first-round victory, while Feliciano Lopez, Tommy Haas, Jeremy Chardy and Jiri Vesely - who knocked Djokovic out in round two 12 months ago - were among the notable names to progress.