Barcelona produce sensational comeback to beat Celta Vigo
The Catalans entered the final 10 minutes two goals down after Jorgen Strand Larsen and Anastasios Douvikas struck for the visitors, who seemed on course for a surprise win against the champions.
However veteran striker Lewandowski netted twice within five minutes to pull Barcelona level and Cancelo sprinted into the box to fire home decisively in the 89th minute.
Wily Celta coach Rafa Benitez set up in his typically defensive fashion, unlike Barcelona's recent visitors Real Betis and Royal Antwerp, whose attacking intent made them lambs to the slaughter.
Barcelona hit 10 goals in their previous two matches, with their coach Xavi saying it was the best they had played in his reign, but this performance was largely at the other end of the spectrum.
"I was making a lot of technical errors, that's not normal in my game - I have to improve, we all have to improve," Cancelo told Movistar.
"It's always better to play badly and win, than to play well and lose, the three points are the most important thing."
The hosts controlled the opening stages, albeit without creating much danger, but Celta Vigo pushed ahead against the run of play after 19 minutes.
Andreas Christensen played Strand Larsen onside after a corner was only partially cleared, and the Norwegian forward finished clinically past Marc-Andre ter Stegen.
Joao Felix could not control a nicely scooped Frenkie de Jong through pass, before the Dutch midfielder sustained a knock and was replaced by tenacious teenager Gavi.
Celta had a fine chance to score the second but Ter Stegen palmed away Strand Larsen's header and Lucas de la Torre slashed the rebound over with the goal gaping.
Xavi shuffled his pack at half-time, bringing on Ronald Araujo for his first appearance after a hamstring injury, as well as 16-year-old winger Lamine Yamal.
Araujo stung the palms of Ivan Villar with a powerful drive from distance and Ferran Torres wasted a fine chance, firing wide as he ran through on goal.
Ter Stegen made another fine save to thwart Jonathan Bamba as Celta sought a second.
Eventually, it came through new signing Douvikas, who swept home after running onto Iago Aspas's perfectly weighted ball.
Quick comeback
Barcelona hit back swiftly, with Lewandowski flicking the ball over the head of Villar and in off the crossbar after Felix cleverly chipped a ball to him over the top.
It sparked a fire previously lacking in Barcelona's performance, with Lewandowski netting the second four minutes later after Cancelo cut the ball back into his path.
The on-loan Manchester City defender has made a quick impact since his arrival on the last day of the summer transfer window and is not afraid to drive forward in search of attacking opportunities.
Cancelo found one to win Barcelona the game, dispatching Gavi's cross past Villar with the prowess of a striker.
"We played a defensive game and the counterattacks worked very well, but Barcelona are used to playing like that and from the 80th minute, tiredness caught up with us," Celta defender Oscar Mingueza, formerly of Barcelona, told Movistar.
"What we can't do is let a game that we went two goals up in slip away in this way."
