Former champions Rafael Nadal, Roger Federer and Juan Martin del Potro are back at work on Labor Day in fourth-round matches at the 2017 US Open on Monday.

Nadal returns to Arthur Ashe Stadium against unseeded Alexandr Dolgopolov.

The No. 1 seed is bidding for his seventh US Open quarter-final appearance and first since winning the 2013 title.

Dolgopolov is 1-8 against players ranked No. 1, posting his lone win over Nadal in a final-set tie-break at 2014 ATP World Tour Masters 1000 Indian Wells.

Though he lost his first five matches and 10 sets against Nadal, Dolgopolov has beaten the Spaniard in two of their past three meetings, adding a grass-court win at 2015 London/Queen’s Club.

After improving to 17-0 against Mikhail Youzhny and 13-0 against Feliciano Lopez, Federer takes an 11-0 FedEx ATP Head2Head advantage into his meeting with Philipp Kohlschreiber.

Federer’s win over Lopez lifted his record in Arthur Ashe Stadium night matches to 31-1.

Kohlschreiber entered the US Open without a hard-court match since March 26 at ATP Masters 1000 Miami.

He received the No. 33 seed and moved to the top half of the draw after No. 2 seed Andy Murray withdrew.

Kohlschreiber has not dropped a set, holding in 37 of 38 service games and saving 16 of 17 break points against three players ranked outside the Top 100.

The German is 1-34 against Top 3 opponents (d. No. 2 Nadal in 2012 Halle QF) and 1-8 in fourth-round matches at Grand Slams (d. Baker at 2012 Wimbledon).

Andrey Rublev, 19, hopes to become the youngest US Open quarter-finalist since Andy Roddick in 2001 when he faces No. 9 seed David Goffin on Louis Armstrong Stadium.

The Russian teenager is 12-4 in his last 16 tour-level matches, breaking into the Top 100 on June 26 after reaching his first quarter-final at Halle and cracking the Top 50 on July 24 after winning his first title at Umag.

Like Rublev, Goffin is seeking his first US Open quarter-final.

Del Potro meets World No. 8 Dominic Thiem on Grandstand in a rematch of the 2016 US Open fourth round.

The 2009 champion advanced last year when Thiem retired in the second set with a right knee injury.

Del Potro is 0-6 versus Top 8 opponents this season after going 5-4 against them in 2016.

Thiem, who celebrated his 24th birthday on Sunday, is one of two men’s players to reach the fourth round at all four Grand Slam events in 2017 (also Nadal).