Coach Ernesto Valverde said Messi was undergoing medical exams.
It may be impossible to definitively judge who is the better player until they have both retired and we have perspective. We will wait. I imagine it's nothing, but we'll wait a few hours. Regardless of what tests say, if the player doesn't think he's ready, you have to leave him out, ' Valverde said.
Suarez also failed to find the net in his only meeting against Los Blancos with another club, finding himself on the end of a 4-0 thrashing in November 2010's Champions League group tie at the Amsterdam ArenA.
Lionel Messi dragged Barcelona back from two goals down by scoring twice to snatch a 2-2 draw at home to Valencia in a thrilling encounter on Saturday night which interrupted the Spanish La Liga football leaders' streak of eight consecutive league wins.
'I'm not in favour of taking risks with so many games coming up, if the season finished tomorrow, it would be another matter.
Real coach Santiago Solari hopes the Barcelona captain is fit to face his side in the first leg for the good of the game, but added the Argentine's presence would not affect his game plan. Valverde said the Frenchman trained separately on Monday and was set to join the rest of the squad for Tuesday's session.
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Brazilian defender Marcelo is the second player Juventus will want to sign, and his signing is expected to make Ronaldo happy considering how close he is with Marcelo in Spain.
Valverde admitted he might have to rotate his line-up given the number of important games coming up.
He's bagged a ridiculous 21 league goals from only 20 games, as well as six goals in the Champions League.
The Nou Camp club have already humbled Real once this season - stuffing them 5-1 back in October.
"They are usually strong at Camp Nou, they play well here. We expect the best version of Madrid on Wednesday, as we have seen in recent weeks".