Big scares for Djokovic and Federer at French Open

(CNN) -- While Rafael Nadal was celebrating his 26th birthday, the two biggest threats to his hopes of a record seventh French Open title were battling to stay in the tournament.

World No. 1 Novak Djokovic came from two sets down on Court Philippe Chatrier on Sunday to salvage his hopes of becoming the first man since Rod Laver in 1969 to hold all four grand slam titles.

On Court Suzanne Langlen, 16-time grand slam champion Roger Federer fought back after losing the first set to a player who idolized him as a child and only gained entry into the main draw as a lucky loser from qualifying.

Both advanced to the quarterfinals ahead of Nadal, who will take on Argentine 13th seed Juan Monaco on Monday.

Jaded No. 1 Azarenka crashes out in Paris

The last time Djokovic came from two sets down was against Federer in the U.S. Open semifinals in September, when the Serbian won his fourth major title.

Spirit, fitness and David Ferrer

Michael Chang's historic French victory

Brian Baker's grand slam comeback

Gilles Simon's endurance advantage

Since then he has added a third Australian Open to his collection, but his form in 2012 has not reached the stunning heights of last year -- when his 43-match winning run was ended by the Swiss veteran in the semifinals at Roland Garros.

"I played very badly, but I won thanks to my fighting spirit," Djokovic said after struggling to beat Italy's world No. 25 Andreas Seppi 4-6 6-7 (5-7) 6-3 7-5 6-3 in more than four hours on Sunday.

"He was the better player for the first two sets and I was fortunate to come through. But even at two sets down I still believed I could do it, and that's about the only positive I can take. It was one of those days when nothing worked."

Seppi, appearing in the fourth round of a major for the first time, had won only two sets in losing their seven previous meetings.

Nadal ready for first real test at Roland Garros

Djokovic will next take on either French fifth seed Jo-Wilfried Tsonga or Swiss No. 18 Stanislas Wawrinka, having reached the last eight of a grand slam for the 12th consecutive time.

Tsonga led 6-4 7-6 (8-6) 3-6 3-6 4-2 in a virtual repeat of his clash with Wawrinka last year when play was suspended due to fading light.

Federer is through to his 32nd successive quarterfinal after beating 21-year-old Belgian debutant David Goffin 5-7 7-5 6-2 6-4.

The 30-year-old is now tied with American Andre Agassi on 36 last-eight appearances, leaving them second equal overall behind Jimmy Connors' record of 41.

He will next take on either Czech seventh seed Tomas Berdych or 2009 U.S. Open champion Juan Martin del Potro of Argentina -- who led 7-6 (8-6) 1-6 6-3 when play was halted long before the Tsonga-Wawrinka match, despite appearing to struggle with a strapped-up knee.

"I thought he played really well. Great impression," Federer said of his young opponent. "He took the ball early every time.

"He's got great potential in terms of his touch and the way he reads the game. I thought it was an interesting match."

Goffin, who told the crowd after the match that he had pictures of Federer on his wall as a child, was ranked 109th in the world when the clay-court tournament started but he will be up to 68th when it ends next Sunday.

He won his first two qualifiers but was beaten in the third before a late reprieve after home hope Gael Monfils pulled out due to injury.

"I came out of the qualifiers and I played my best tennis in my first three matches. Then playing Roger was the cherry on the cake," Goffin said.

"I won't hide the fact that I had photos of Roger everywhere on the walls of my bedroom. It was like a dream for me playing him here."

Goffin stunned Czech 23rd seed Radek Stepanek in the first round proper, then beat more experienced opposition in veteran Frenchman Arnaud Clement -- playing his home tournament for the last time -- and Poland's Lukasz Kubot.

He was the first lucky loser to reach the last 16 of a grand slam since compatriot Dick Norman did so at Wimbledon in 1995.