MADRID, April 17 (Xinhua) -- FC Barcelona coach Ernesto Valverde commented to the press that Leo Messi was "unstoppable" after the Argentinean netted the two goals that helped book Barca's place in the semifinals of the Champions League for the first time since 2015.

It was hard to imagine that Messi hadn't scored in the last eight of the competition since 2013 as he opened the scoring in Tuesday night's 3-0 win at home to Manchester United with a precise left foot shot from outside of the area in the 16th minute of the game.

Four minutes later he did something similar with his right foot (all be it with the aid of some poor goalkeeping from David de Gea) and Barca's place in the last four was secure.

Messi was also involved in most of Barca's best moments as they cruised past United, rarely looking in danger after weathering a difficult opening 10 minutes when United looked to put them under pressure.

Once their rivals ran out of steam, Messi and Barca controlled the show and their rivals didn't have a scoring chance until injury time.

"We gave a spectacular image in the game: this is what we are," said Messi after the game on Spanish TV.

"We were nervous and slow in the opening five minutes, but after that we controlled the game and played some spectacular football," he said.

Messi was humble when asked about his two goals saying "I was lucky that the first one went in as it was close to the post and the second was a even more fortunate. But we have taken another step forward," he said.

Messi remembered last season's disappointment when Barca crashed out of the quarterfinals with a 3-0 defeat to Roma after leading 4-1 after the first leg.

"We had the experience from Rome to show how a Champions League game can escape you in five or 10 minutes," he commented, adding that he didn't mind whether Barca face Liverpool or Porto in the semifinals.

"It's a semifinal, the two sides that deserve to be there will face each other and it will be tough," he commented.