Barcelona open their Champions League title defence against a familiar face when they tackle José Mourinho's Inter Milan at San Siro.

Assistant to Bobby Robson at Camp Nou in the late 1990s when Barcelona coach Pep Guardiola was an influential midfielder, Mourinho has since won the Champions League with FC Porto, two English league titles with Chelsea and Serie A with Inter.

Now he comes face to face with Guardiola, who last season, guided Barca to the domestic league and cup titles as well as the Champions League.

Tomorrow's game could also see Barcelona striker Zlatan Ibrahimovic and Inter's Samuel Eto'o facing each other, a season after they played for each other's clubs.

"A player that gave me as much as Ibra will always be in my heart, but I'm someone who forgets quickly and I'm focusing on my current players now," Mourinho said on Sunday. "We'll exchange a big hug before the game but, during the match, I don't even want to know who he is. He did a lot for Inter and Inter did a lot for him."

Eto'o, who scored Inter's first goal in Sunday's 2-0 victory over Parma, said Inter ought not overestimate the game against his former club.

"Inter-Barcelona will be an important game for Inter because it's the first in the Champions League, but I think all the games are important."

Barcelona and Inter are the strong favourites to qualify for the last 16-team knockout stage from their group and leave Dynamo Kiev and Russian champion Rubin behind. They meet tomorrow in Ukraine.

Arsenal, Liverpool, Chelsea and Manchester United - the last four Champions League runners-up - are back again, while United won the title in 2008.

Manchester United begin the group phase away to Turkey's Besiktas today and also have surprise German champion Wolfsburg and CSKA Moscow in its group.

Now guided by Carlo Ancelotti, who won the title with Milan as a player and a coach, Chelsea begin against FC Porto. The two clubs also have to face Atletico Madrid and APOEL Nicosia, who also meet today.

Arsenal go to Standard Liege tomorrow when group rivals Olympiakos and AZ Alkmaar also meet. The Gunners come off their second Premier League loss in a row - 4-2 at Manchester City - while Standard will be without captain Steven Defour, who broke his right foot in a league game on Saturday.

Five-time winner Liverpool host Hungarian Debrecen, which make their first visit to Anfield tomorrow. Lyon, which have won six games in a row, meet Fiorentina in the other group match.