Messi made it 2-0 in the 59th minute, dribbling between a defender's legs before slotting home – Xavi had opened the scoring two minutes before half-time.
Barcelona's players wore T-shirts before the game with messages of support for Vilanova, who had throat surgery to remove a second tumor in two years on Thursday.
Barcelona maintained their perfect away record with a ninth win on the road, and extended their record league start with their 16th victory in 17 games to open up a nine-point lead over second-placed Atletico Madrid.
Andrews brace not enough
Peterborough's flying start proved decisive as they edged Bolton in a nine-goal thriller at London Road.
Buoyed by their surprise victory over leaders Cardiff last week, Posh raced into a two-goal lead inside six minutes thanks to Lee Tomlin and Dwight Gayle. Ireland midfielder Keith Andrews reduced the arrears from the penalty spot but George Thorne's drive made it 3-1 after half-time.
Another Andrews spot-kick prompted Bolton's most promising period but Peterborough defenders Mark Little and Gabriel Zakuani got in on the act to apparently make the points safe.
But there was a final twist as Bolton subs Benik Afobe and Martin Petrov netted inside the final six minutes to set up a grandstand finish.
Victory for Barnsley at Millwall, and Bristol City's draw at Ipswich means Darren Ferguson's side remain bottom of the table, while Bolton head into Christmas eight points shy of the play-off places in 16th.
Becchio scored either side of the break to cancel out Lucas Jutkiewicz's opener and earn his side a fifth win in six Championship games. He hoisted his tally for the season to 17 and his recent scoring spree to seven in seven league and cup games – but a new striker is still on Warnock's wish-list.
"Luciano's first goal was unbelievable. It was a top-quality finish,'' said Warnock. "I still feel we need another striker because Luciano can't play week in, week out, with so many games coming up and we need someone in case he gets injured. That has to be my priority.''
Owls fly out of bottom three
Rhys McCabe struck his first senior goal and Jeremy Helan was also on target as Sheffield Wednesday registered a 2-0 victory which saw them climb out of the bottom three of the Championship with a second successive win.
Scottish midfielder McCabe, a summer signing from Rangers, slammed home a superb volley from the edge of the area midway through the first half and Frenchman Helan marked his final game for the Owls before his return to parent club Manchester City with a late second.
Charlton, who lost their first league game in eight at Bolton last week, turned in a disappointing display and mustered only two efforts on goal.
Tudgay winner stuns Millwall
Marcus Tudgay's late goal saw Millwall slip out of the play-off places after a surprise 2-1 defeat at home to Barnsley, who gave their Championship survival bid a welcome boost.
Tudgay struck in injury-time after Chris Wood appeared to have salvaged a point for the Lions, who had lost just once in their previous 16 matches. Barnsley led through a first-half goal from Stephen Dawson, shortly after Millwall's Darius Henderson had missed a penalty.
Bellamy takes Cardiff clear
Cardiff bounced back from their surprise home defeat to Peterborough with a smash-and-grab 1-0 victory at Leicester to move three points clear at the top of the Championship.
Leicester laid siege to the Bluebirds' goal in the first half with chance after chance going abegging.
Craig Bellamy looked a threat on the counter-attack throughout and he grabbed the only goal of the game against the run of play after 25 minutes. The Wales star showed great technique after collecting Craig Conway's pass to find the bottom left-hand corner from 12 yards.
Watford back in play-off spot
Matej Vydra scored twice as Watford moved into the Championship play-off places with a 2-0 victory over Nottingham Forest.