Roger Federer set up a 24th career meeting against old rival Andy Roddick as both men eased through the Miami Masters second round, but crowd favourite Kim Clijsters crashed out of the women's event.
Third-seeded Federer, who has a 21-2 record against world number 34 Roddick, on Saturday recorded his 23rd win of 2012 by beating 19-year-old American wild card Ryan Harrison 6-2, 7-6 (7/3).
"I felt like I had to win the match like three times at the end, so I was relieved to come through," Federer said. "And beating an American in America is always a big deal, because this is here where they usually play their very best."
The Swiss superstar is bidding to capture his third Indian Wells-Miami title double, having also won the back-to-back US hardcourt Masters events in 2005 and 2006.
Federer has now won 40 of his past 42 matches since the 2011 US Open semi-finals.
"I guess I'm more confident now. I have been playing really nice as of late," Federer said.
The American, who is at his lowest ranking since July 2001, won in 74 minutes.
Monfils next faces Argentine 21st seed Juan Monaco.
In the women's event, former world number one Clijsters saved three match points but lost 6-4, 7-6 (7/5) to Belgian compatriot Yanina Wickmayer, the 23rd seed, in the third round.
"She definitely started off much better and was more consistent throughout," Clijsters said. "It was close. It's a little bit frustrating knowing that I am playing not even 50 percent but it is still that close.
"On one hand I could have beaten her with the way that I was playing and feeling, but she played good."
Clijsters, who was playing her first tournament since an Australian Open semi-final defeat by Azarenka, had skipped last week's Indian Wells tournament to rest her injured ankle.
The 28-year-old won the Miami event in 2005 and 2010.
Williams, who is playing her first tournament since a fourth-round exit at the Australian Open, will face either Australian sixth seed Samantha Stosur or South Africa's Chanelle Scheepers for a place in the last eight.
Source: AFP Global Edition