Monte Carlo: Roger Federer made a flawless comeback after two and a half months away, as the Swiss advanced over Guillermo Garcia-Lopez 6-3, 6-4 on Tuesday to power into the third round of the Monte Carlo Masters.
But it was a struggle for number two Andy Murray, who needed to call upon all of his resources to survive his opening match of the season on clay.
The Scot scratched out a narrow 6-2, 4-6, 6-3 win over French qualifier Pierre-Hugues Herbert.
Federer showed no signs of a layoff after undergoing a knee operation on 3 February and delaying his comeback by three weeks due to stomach illness last month before Miami.
Federer has never won the Monte Carlo title, losing in four finals, most recently in 2014 to compatriot Stan Wawrinka, the reigning French Open champion.
He said his repaired knee gave him absolutely no trouble: "The knee felt really good, like in practises, it felt like I didn't have to worry about it. I'm at a point now where I'm looking more forward in the sense that whenever I can dig out a good point,
"It's only building on my confidence now, which is great."
Federer was broken while serving for the win leading 5-2 in the second set; he got the job done on the second time of asking with a winner.
Federer called the win "in a way, the perfect match."
"It was close in the beginning, then I was able to go on a roll. Points were cut short by virtue of me serving better and returning better, getting second serves, taking advantage of that fact.
"At the end, again, I had to fight for it. I was excited and tense in the beginning just because it's a first round. It's my first match back. So it was nice to go through all these emotions.
"I think I got what I needed. So we'll see how I feel tomorrow, tonight, the next day. Sometimes after a match, you can feel it for two days. At this point I'm pretty confident I'll feel fine."
Federer, playing here for a 13th time, won his fourth match over Garcia-Lopez without the loss of a set as they met for the first time on clay; he claimed his 29th Monte Carlo match win.
'Little bit flat'
Murray needed two hours to book his place in the third round after losing serve four times against Frenchman Herbert.
The Scot has yet to regain his top form two months after becoming a father.
"I've definitely been a little bit flat since the Davis Cup (last November). I don't know why. In a lot of my matches, it's been some good stuff mixed in with some pretty bad stuff.
"The norm is bad just now, so I need to improve on that. I'm not playing my best. The consistency has not been there, maybe not as sharp as I could be mentally.
"It was obviously a very scrappy match. The best tennis I played was really in the third set when I was up a break," Murray said. "He had a few chances there. I was able to raise my game at those moments.
"It was up and down in the second set for me, on this surface, that's something that shouldn't happen. I made too many mistakes."
The 28-year-old has a massive set of clay-court ranking points to defend after last year winning his first two titles on the surface at Munich and Madrid.
Murray improved his tournament record to 12-7 with the victory. He needed to battle in a tight third set against the 95th-ranked Herbert, breaking to love for a 3-1 lead that proved decisive.
Spain's injured seventh seed David Ferrer withdrew a day prior to his second-round match against German teenager Alexander Zverev. He was replaced by compatriot Marcel Granollers.
Ferrer, a finalist in the Principality five years ago against Rafael Nadal, has had a patchy 2016 season, taking a break from late February to late March to rest.
Upon his return, the ATP number eight lost in the Miami third round to France's Lucas Pouille.
Simon, Tsonga advance
Frenchman Gilles Simon also earned a second-round win, beating Bulgarian Grigor Dimitrov 6-4, 6-3 while French eighth seed Jo-Wilfried Tsonga defeated Pablo Carreno Busta 7-6 (7/1), 7-6 (7/5).
In the first round, Belgian 11th seed David Goffin dispatched Feliciano Lopez 7-5, 6-0, while Portugal's Joao Sousa beat Ivo Karlovic 6-3, 7-6 (7/4),
Bosnian Damir Dzumhur put out Robin Haase 6-2, 6-0 and Pablo Cuevas needed three hours 20 minutes to defeat Daniel Gimeno-Traver 7-6 (7/2), 6-7 (2/7), 7-6 (7/4).