Barcelona's French defender Jeremy Mathieu celebrates after scoring against Celta de Vigo in their Spanish league match at the Balaidos stadium in Vigo on Sunday. (AFP)

DPA/Madrid

A late 1-0 win on Sunday at midtable Celta Vigo maintained Barcelona’s four-point lead atop the Spanish Liga.
Barca needed a goal 16 minutes from time from defender Jeremy Mathieu—who headed in a free-kick from supersub Xavi—to break the spirited resistance of well-drilled Celta.
The hosts were the better team in the first half but were foiled by Barca goalkeeper Claudio Bravo, then had two good penalty claims turned down.
Barca took control in the second half and should have gone ahead when Neymar had a goal disallowed for what looked like a non-existent offside.
Celta had midfielder Fabian Orellana sent off three minutes from time for unsporting behaviour.
“It was a very complicated match. Things are always difficult after the
break for the international matches,” Mathieu said.
“Celta were better than us in the first half, but the important thing is that we took the three points. It was wonderful to score the winning goal.”
Celta striker Nolito said: “We really should have taken the lead in the first half, then it would have been a very different game.
“We let them off the hook, and against a team of their quality that is something that you just cannot do.”
Barcelona’s outlay of 20 million euros ($22 million) on Mathieu last July prompted plenty of criticism but the France centre-back has been worth his weight in gold in the La Liga leaders’ last two outings.
After scoring the opener in Barca’s 2-1 win over second-placed Real Madrid in the ‘Clasico’ two weeks ago, it was Mathieu again who scored the only goal in Sunday's laboured win.
Mathieu, who was signed to strengthen a defence that repeatedly let the club down last season, also put in an accomplished performance alongside Gerard Pique at the back as Barca kept their 16th clean sheet in 29 La Liga games this term.
“I scored two important goals, I am pleased,” Mathieu said. “Sometimes you have to suffer when you win,” added the 31-year-old, who joined Barca after a five-year stint at Valencia.
“It was a very tough match. After the international break it’s more difficult as your rhythm always drops a bit.”
Luis Enrique’s side are also through to the last eight of the Champions League to face Paris St Germain and will play Athletic Bilbao in the King’s Cup final at the end of May.
Victory in all three competitions would match the club’s unprecedented treble in 2009 under Pep Guardiola.
“It could be that we are fresher because a lot of players (in the squad) are used here,” Mathieu said. “That is very important for the final stages of the season. We are on the right track and now we have to think about the next match.”
Barca have La Liga games at home to Almeria and away at Sevilla before they play at PSG in their quarter-final, first leg on April 15.
Sunday's win left Barca with 71 points from 29 games, four more than second-place Real, who earlier crushed hapless Granada 9-1 as Cristiano Ronaldo notched the first five-goal match of his illustrious career.
Real are five points above third-place Atletico Madrid, who beat bottom team Cordoba 2-0 Saturday.
Valencia are a point below Atletico in fourth place, after a disappointing 0-0 draw at home to sixth-place Villarreal.
Also on Sunday, midtable Getafe beat struggling Deportivo Coruna 2-1.