NEW YORK—Maria Sharapova insists she's not a night person, but after extending her perfect record in U.S. Open evening matches, there's clearly no need for the early riser to recalibrate her body clock.

Sharapova burst out of the blocks quickly and accelerated through the finish line in subduing Sabine Lisicki, 6-2, 6-4, to reach the U.S. Open fourth round for the fifth time. The 2006 U.S. Open champion raised her record in Flushing Meadows night matches to 18-0.

Facing the powerful German who blasted the fastest recorded serve in WTA history (131 M.P.H.) last month, Sharapova hovered on the baseline and pounded her returns, breaking six times and winning 16 of 23 points played on Lisicki's second serve. She set the tone for the match early, breaking for a 2-0 lead.

The fifth-seeded Russian was pushed to deuce in her first four service games, but refused to crack. Former Wimbledon finalist Lisicki is an aggressive baseliner, but she struggled to land shots between the lines in the first set, badly missing a backhand down the line on a break point in the seventh game. Attacking the net, Lisicki mis-judged a defensive lob from Sharapova and let the ball pass, believing it would float long. The shot landed well inside the baseline as Sharapova worked out of a 0-30 hole to hold for 5-2. When Lisicki clanked her third double fault, Sharapova snatched the 40-minute opening set.

Three straight breaks marked a scratchy start to the second set as both women struggled to clear the net. Sharapova, who caught her unruly toss several times, littered three double faults in dropping her first two service games to trail 1-2. Serving to consolidate, Lisicki hit her fifth double fault and compounded that miscue flattening a forehand into net to face break point. Then she made a pair of tremendous corner-to-corner retrievals, lofting back lobs on the dead run. Sharapova, who is averse to hitting traditional overheads, opted instead for a high forehand, only to belt the ball long as the No. 26 seed held for 3-1 with a hearty fist pump.

Before Sharapova served to start the fifth game, chair umpire Carlos Ramos warned Lisicki, "your coach needs to stop giving you signals...We'll talk on the changeover." Lisicki crushed a forehand swing volley winner to earn break point, but a stubborn Sharapova saved it, eventually holding with an inside-out forehand winner for 2-3. Perhaps Lisicki was still rattled by the exchange with Ramos or maybe she was merely overzealous in an effort to make a statement shot, but when she swooped in for another swing volley, she sailed it beyond the baseline to hand back the break for 3-all. An inside-out forehand winner gave the Russian her third break of the set for a 5-3 advantage.

Sharapova's style isn't always pretty—her serve can go kablooey (she hit eight double faults), her flat forehand can expire in a collision course with the net, and her shrieking can sometimes degenerate into piercing wailing—but even when she lacks grace she compensates with guts and exhibits the courage to take the bold strike regardless of the score or stress level.

Failing to serve out the match at 5-3, Sharapova simply shrugged it off as a temporary setback. Sprinting after every ball with vigor, Lisicki saved two match points in the ensuing game. Sharapova punished an 87 M.P.H. serve with a crunching return winner down the line for a third match point and concluded a hard-fought clash shortly after midnight. She will face former No. 1 Caroline Wozniacki for a spot in the quarterfinals.

"You have no choice but step it up when it counts if you want to continue and ultimately be the champion of this event," Sharapova told ESPN's Darren Cahill after the match before revealing her plans for the rest of the night.  "Maybe get a good night hug from someone," she said, referring to boyfriend Grigor Dimitrov, who swept Dudi Sela during the day session. "Hopefully [he's] sleeping."