United favourites at home against Braga

Manchester United's determination to avoid last season's mistakes, a winning start this term and their unbeaten home record against Portuguese teams are good signs ahead of Braga's Champions League visit on Tuesday.

Although Braga are unbeaten in their last five games against English sides, United look to have too much in attack, especially with Wayne Rooney re-discovering his scoring form after a slow start to the season.

United go into the match top of Group H with six points after wins over Galatasaray and CFR Cluj, in stark contrast to the sluggish start they made to last season's competition when they drew their opening two games and eventually failed to make it out of the group stage.

Braga lost at home to Cluj in their opening match before bouncing back with a win at Galatasaray to keep alive their hopes of advancing to the knockout rounds, but they will do well to leave Old Trafford with a point.

United's defence has not been as watertight as usual, conceding five goals at home in their last two Premier League matches against Tottenham Hotspur and Stoke City, but their attack has fired in 26 goals in all competitions so far.

Dutch striker Robin van Persie has scored five Champions League goals in his last five matches for Arsenal and United and was also on target against Stoke on Saturday.

Elsewhere, Celtic will have to reverse a horrible record in Spain and cope with a Bar­celona side fired by the scintillating form of Lionel Messi if they are to reap an unlikely reward from Tuesday's Group G clash at the Nou Camp.

The Scottish champions, second in the group behind the 2009 and 2011 winners after two matches, have never managed a win on 12 trips to the Iberian nation, slumping to nine defeats and three draws.

Favourites Barca are unbeaten in 17 European home outings, winning 14, going back to a 2-1 defeat against Rubin Kazan in October 2009.

Their Argentine World Player of the Year Messi, top scorer in Europe's elite club competition the past four seasons, netted his 21st hat-trick for the club on Sunday in a 5-4 La Liga win at Deportivo Coruna.

The unstoppable 25-year-old took his tally in 2012 for club and country to 71, leaving him only four short of the record of 75 set by Brazil great Pele in 1959.

Barca coach Tito Vilanova has some selection problems, with a suspension for Sergio Busquets coming on top of injuries to centre backs Carles Puyol and Gerard Pique and right back Daniel Alves.

Real Madrid visit Dortmund, who have reversed last season's pattern of struggling in Europe and doing well in the Bundesliga. Bayern, who suffered a shock 3-1 defeat at BATE Borisov, visit Lille in Group F while the Belarus champions host Valencia. Manchester City, who have one point in Group D, visit Dutch champions Ajax Amsterdam.

Ambitious Russian clubs Zenit St Petersburg and Spartak Moscow go in search of their first Champions League points this week as they attempt to improve their country's unimpressive record in the competition.

This week's third round of matches, where Real Madrid's visit to Borussia Dortmund is the highlight, is also potentially decisive for the hopes of Manchester City, Juventus and Benfica, who have yet to win a game between them.

Zenit will finally hope to get off the mark against Belgian champions Anderlecht, who have one point, in Group C on Wednesday, where Malaga (6) and Milan (4), who meet in Spain, are already looking the likely qualifiers despite the Serie A side's domestic troubles.

Serie A champions Juventus drew their opening two games in Group E but should win Tuesday's match away to Nordsjaelland. The Danish champions were out of the their depth as they lost 4-0 at home to titleholders Chelsea, who visit Ukrainian champions Sha­khtar Donetsk with both teams level at the top on of the group on four points.