Sir Alex Ferguson says he will have to reassess how he approaches European games at Old Trafford after Manchester United's performances this season.
United have usually been solid at home going unbeaten in 23 games between 2005 and 2009 and were unbeaten at home in Europe last season as they reached the UEFA Champions League final.
However this season they have managed only one win in their five home games in the Champions League and Europa League.
On Thursday night, Athletic Bilbao came from behind to lead 3-1, before a late Wayne Rooney penalty made it 3-2 to give United some hope for the second leg.
"We have had a bad year in Europe," Ferguson said.
"We conceded three against Basel, two against Benfica, another three against Bilbao and two to Ajax. That tells its own story.
"Maybe it is just one of those years where we are having to restock and assess how we should approach games at home."
Michael Carrick, who came on as a second-half substitute in Thursday's defeat for the injured Chris Smalling, conceded that the team as a whole must do better.
"We have been giving the opposition too many chances, which tells a tale," said Carrick.
"That is not just putting the blame on the defence, it is the team as a unit. We have to defend right altogether. That hasn't been the case."
The Red Devils cannot spend too long lamenting the result however, as West Brom travel to Old Trafford on Sunday, a game United must win to keep the pressure on at the top of the league.
"We are desperate to win the league again and Sunday is the next game," added Carrick.
"It is massive, as they all are, and we will be ready for it."