Andy Murray was slow to overcome Gilles Muller on his return from injury to reach the third round of the Monte-Carlo Masters.
The world No1 has been sidelined with an elbow problem since March 12 and his serve continued to be affected in the early stages as three double faults in the first four points of the match got him into early trouble.
He then had to save a set point before reeling off four games in a row and, despite continuing to play some way below his best, battled through the second set to win 7-5 7-5.
Murray has significantly extended his lead over Novak Djokovic at the top of the rankings despite a slow start to the season but has a huge amount of ranking points to defend from now until the end of the year.
Clay has been very profitable for the Scot over the last two years having previously been by far his weakest surface.
Luxembourg's Muller, who was previously guided by Murray's assistant coach Jamie Delgado, is a serve-volleyer and not a typical clay-court opponent.
That seemed to be a positive thing for Murray, who had won all five of their previous meetings, but the 29-year-old made a decidedly ropey start.
Muller, a top-30 player for the first time aged 33 and one of tennis' flourishing old guard, missed a chance to take the set at 5-3, and that gave Murray the spark he needed as he broke back to love.
And two games later Murray completed the turnaround by winning the set when Muller missed a simple volley, smashing his racket in frustration.
After an exchange of breaks at the start of the second Murray missed several openings as he struggled to find any consistency.
But a bit of the old Murray magic brought up his first match point with a backhand dinked across the court and he took it when Muller blazed a forehand wide.
The top seed next faces Spanish 15th seed Albert Ramos-Vinolas.
Murray told Sky Sports: "It was a tough first match, I started the match pretty slow, I obviously wasn't serving that well at the start.
"I haven't been in the best rhythm on serve because I only started serving at full speed four or five days ago. I knew it would take a bit of time but I wasn't expecting to start serving like that.
"It got a little bit better, I started to create a lot of chances in the second set. I couldn't get the breakthrough until right at the end."
Ahead of Thursday's clash with Ramos-Vinolas, Murray said: "He's always a tough guy to play against. I've practised with him quite a bit, he obviously likes the clay.
"He's a lefty as well so it's good I got some practice in. It's a completely different match-up and I'll need to be ready for a big fight because he doesn't give anything for free."