Madrid - Tuesday will be do or die time for troubled Barcelona. Their brilliant but brief reign as champions of Europe could be over unless they beat the Italian champions at home.
Never in the history of the Champions League have the defending champions failed to qualify from the group stage the following season. But this is exactly what could happen to Barca unless they win on Tuesday.
Their situation in hard-fought Group F is precarious, to say the least.
They are in third place, level on five points with Rubin Kazan. Inter are top on six, Dynamo Kiev are bottom - though still in with a shout - on four.
On Sunday Barca coach Josep Guardiola said that "the game (against Inter) is very important and, in spite of everything, we will do well."
Guardiola expressed the hope that the massive Camp Nou "will be full, without a single seat empty."
Midfielder Sergio Busquets - one of the many youngsters given his wings by Guardiola - said that "Tuesday's game will be like a final and we have no choice but to win."
Just five months ago Guardiola's team were the toast of Planet Football after sweeping to an unprecedented "triple" of Spanish league, cup and Champions League.
But now they are close to Euro elimination and second in La Liga, one point behind deadly rivals Real Madrid.
The question being asked right now by football fans all over the globe is: what has gone wrong since then?
Guardiola raised eyebrows by swapping top scorer Samuel Eto'o for Inter's Zlatan Ibrahimovic in July.
The gamble seemed to be paying off up until three weeks ago, as Ibrahimovic scored seven goals in La Liga. But the mercurial Swede has been out of action since the beginning of November with a torn muscle in his left thigh and will miss Tuesday's match against his old team.
The injuries that have plagued Barca this season are the principal reason for their decline.
Thierry Henry and Rafa Marquez have been in and out with muscle problems, little Andres Iniesta has been a shadow of the force he was last season because of injury.
In addition, Lionel Messi has been in flat form - possibly because of the criticism he has received for his displays for Argentina - and is doubtful for Tuesday's clash with a similar problem to Ibrahimovic's.
To make matters worse, Marquez, Eric Abidal and Yaya Toure are all laid up with swine flu.
"We cannot use these injuries and illnesses as an excuse," said Guardiola after Saturday's 1-1 draw away to Athletic Bilbao, but the truth is that he has been unable to field his best team all season.
Another factor explaining Barca's problems is that playmaker Xaxi - who was so imperious last season - has been closely man-marked by many rival teams, thus cutting off Barca's slick circulation.
In addition, Guardiola is finding it hard to maintain the hunger and ambition of last season, after his team has picked up so many trophies and has been showered with so much praise.
