Barcelona fear that forward Lionel Messi could be out of action for up to three weeks after sustaining a leg injury against Paris Saint-Germain on Tuesday.

The Argentinian was forced off before the break of their 2-2 draw in the first leg of their Champions League quarter-final clash and is a major doubt to make the return leg next week.

However, assistant manager Jordi Roura is refusing to rule the 25-year-old out of the match until they receive results of a scan that Messi will undergo on Wednesday.

"Messi has a small problem and we don't know how it will affect him until he undergoes the tests [on Wednesday]," Roura told ESPN.

"[His absence would] be a major loss because he is the best player in the world, but we have a big squad, and good players, and will try to win the tie."

Barca will also be without Javier Mascherano for six weeks after he injured his knee in Paris.