LONDON -- It pays to be on guard when Liverpool are preparing to take a set-piece.

Divock Origi's Champions League semifinal-deciding goal against Barcelona last season was the result of a quick-thinking corner by Trent Alexander-Arnold, and it was with similar dead-ball creativity that the European champions fooled Chelsea in a hard-fought 2-1 Premier League win at Stamford Bridge.

Both of Liverpool's goals were scored in the first half and both came from free kicks that saw back-heels change the angle of attack sufficiently to throw Chelsea off-guard. In the 14th minute, after coordination by visiting skipper Jordan Henderson, Mohamed Salah flicked the ball into the path of Alexander-Arnold, who crashed a glorious shot into the top-right corner.

Sixteen minutes later, wide on the left side, Alexander-Arnold nudged the ball to Andy Robertson, who crossed for the unmarked Roberto Firmino to plant an emphatic header past Kepa Arrizabalaga.

Neither of Liverpool's flying full-backs has enjoyed an untroubled start to the season. Alexander-Arnold was criticised for his defensive contributions early in the campaign, while Robertson received so much abuse on Twitter for conceding a penalty in Liverpool's midweek Champions League loss to Napoli that he temporarily deactivated his account.

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But with both players providing decisive contributions at both ends of the pitch, Sunday's trip to west London was more in keeping with the heights they consistently hit last season.

Alexander-Arnold's goal was his first since he curled in a free kick at Watford last November. (His deflected cross that looped in during last month's 3-0 win at Burnley went in the books as a Chris Wood own goal.)

Robertson, meanwhile, supplied his usual quota of dangerous crosses from the left, and it was his name on the lips of the visiting support when the final whistle sounded after a typically powerful surge from deep that drew a booking for Chelsea's Marcos Alonso and sealed the victory.

Because by that stage, the visitors were hanging on after a superb 71st-minute goal by N'Golo Kante, who was making his first appearance since Aug. 18 after overcoming an ankle injury, gave Chelsea hope. The French midfielder surged to the edge of the box and brilliantly steered a shot inside the right post.

Liverpool have kept a clean sheet in only one of their nine games in all competitions this season, and the hosts came close to snatching an equaliser in the dying stages. From two left-wing Alonso crosses, substitute Michy Batshuayi glanced a header wide before Mason Mount swept a shot into the Matthew Harding Stand.

It was a far cry from the first half, when Chelsea gave Liverpool just a couple of scares: Cesar Azpilicueta had a goal chalked off for offside following the intervention of the VAR and Tammy Abraham squandered a one-on-one against Adrian.

Liverpool's 15th consecutive league victory saw the leaders reestablish a five-point lead over Manchester City and made them the first team in English top-flight history to win their opening six games in successive seasons.

A more telling statistic, however, is that this was only the second time Jurgen Klopp's side had won away to one of their Big Six rivals in 13 attempts. Last season's extraordinarily taut title run-in rendered draws every bit as damaging as defeats, and Klopp was delighted to have come through this particular ordeal with three points in the bag.

"It's a difficult place to come, so it feels like a big one," the Liverpool manager said. "The boys fought really hard. I don't think there's any other way to play here."

Defensive concerns continue to beset Klopp's opposite number, Frank Lampard. After seven games in charge, he has yet to see his side keep a clean sheet, while only Norwich and bottom-of-the-table club Watford have conceded more than the 13 shipped by Chelsea.

Moreover, first-half injuries that forced Emerson Palmieri and Andreas Christensen to hobble off will not help matters. Palmieri aggravated a thigh injury, while Christensen took a bang to the knee after playing an unwitting role in both of Liverpool's goals.

His clumsy challenge on Sadio Mane conceded the free kick from which Alexander-Arnold opened the scoring, before Firmino found space between Christensen and Alonso for what proved to be the winner.

"Details lose you games," Lampard said. "The Firmino goal loses us that game because he can't have a free header in our six-yard box."

Nevertheless, the Chelsea boss was heartened by his side's second-half display and praised 21-year-old centre-back Fikayo Tomori for the manner in which he kept Salah quiet.

Lampard is still without a home win but does not feel the quality of his team's performances is fairly reflected by their position in the bottom half of the table. In that respect, he could only look at Liverpool with envy.

"We need to aspire to a level like Liverpool's," he said. "They come here and probably don't play their best, but win the game."