Serge Gnabry fired Bayern Munich to the brink of the Champions League quarterfinals as the German's double inspired a superb 3-0 rout of Chelsea in the last-16 first leg at Stamford Bridge on Tuesday.

Gnabry had tormented Tottenham Hotspur with four goals in Bayern's 7-2 victory in north London earlier this season and the former Arsenal winger returned to the English capital to push Chelsea to the brink of elimination.

The 24-year-old's time with Arsenal was a disappointment and even flopped during a loan spell at West Bromwich Albion.

But he has been reborn with Bayern and his two goals in the space of three minutes left Hansi Flick's side within touching distance of the last eight.

Robert Lewandowski got Bayern's third before Chelsea defender Marcos Alonso was sent off in the 83rd minute.

Chelsea will need another Munich miracle in the second leg on March 18 to overturn the deficit at the Allianz Arena, where they famously beat the German club in the 2012 Champions League final.

This hasn't been a vintage year for Bayern, but they have been energized since the exit of disliked boss Niko Kovac and outclassed Chelsea in all phases.

None of the previous six teams to have won all of their Champions League group games have lifted the trophy that season, but five-time winners Bayern will fancy their chances of breaking that duck if they can maintain this form.

Chelsea boss Frank Lampard admitted his young team were "underdogs" against a club of Bayern's vast European experience and his pre-match prediction proved spot on in a chastening defeat.

"The performance was poor and sometimes you have to be brutally honest. They outclassed us in every department and it's quite sobering," Lampard said.

"I'm disappointed we couldn't do more against them. We have to take it on the chin and work towards getting back to the levels we want to be at."

Bayern set the tone when Thomas Mueller forced a save from Willy Caballero inside the first minute after stealing possession from Jorginho.

Bayern deservedly took the lead in the 51st minute with a superbly crafted goal.

Bayern were irresistible and they increased their lead three minutes later thanks to another impressive combination from the Gnabry and Lewandowski double act.

Lewandowski became the first Bayern player to score in six consecutive Champions League matches when he tapped in from Alphonso Davies's 76th-minute cross for his 39th goal of the season.

Elsewhere, Barcelona drew 1-1 at Napoli in the first leg of the Champions League round of 16.

Dries Mertens tied Napoli's all-time scoring record by curling in a first-half shot and Antoine Griezmann equalized for Barcelona near the hour mark after being set up nicely by Nelson Semedo for the visitors' only shot on target.

Mertens matched former Napoli captain Marek Hamsik with 121 goals in all competitions for the club – six more than Maradona.

Napoli has reached the Champions League knockout stages for the third time in six appearances but has never progressed further than the round of 16.

Key Barcelona midfielder Arturo Vidal – who deputized in attack amid a shortage of forwards for Barcelona – was sent off in the final minutes after picking up two quick yellow cards, first for a hard foul on Insigne then for physical contact with Mario Rui after play had stopped. Already depleted by injuries, Barcelona will also be without Sergio Busquets in the second leg on March 18 due to accumulated cards.

Also, veteran Barcelona defender Gerard Pique limped off with an apparent injury toward the end.

An error from Barcelona left back Junior Firpo led to Napoli's goal, as Piotr Zielinski took control and surged forward before crossing to Mertens, who unleashed a precise shot into the far, top corner.

Minutes later, Napoli nearly scored again when Jose Callejon pulled back for Kostas Manolas, who missed just wide from close range.

Mertens had to come off following a rough foul from Busquets early in the second half that resulted in a costly yellow card for the midfielder.

But Busquets then provided the through ball that led to Griezmnann's goal, with Semedo running in behind Mario Rui to set up the France forward.

On Sunday, Barcelona visits Real Madrid for El Clasico. 

(With input from agencies)