But a foul by Toni Lato led to Messi halving the hosts' deficit six minutes before the interval with a spot kick of his own as the teams went to the dressing room with Valencia leading 2-1.
It is unclear whether Messi, the all-time top goalscorer in Spanish football, as well as in the "Clasico", will be fit for the game.
"Speaking after the game, Barça boss Ernesto Valverde said: "(Messi) has a small problem.
Messi's absence at the Camp Nou would be a blow to Barcelona, particularly with the Argentinian in such blistering form.
"There is a training session and we will see how he is, whether he can do it and whether he is in the right condition. If Messi's ready he will play, if he's not he won't".More news: Kylie Jenner and Travis Scott Tease ‘Baby #2’
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"I hope not, although it is curious to say the least", Solari said.
The ex-Ajax ace has yet to score against Madrid in cup competitions, though, firing blanks in both legs of the Supercopa last season, despite playing a full part in both matches. We'll make a decision based on that.
"Fixtures lists are always hard at this time of year, throughout January, and with this semi-final with two top-level games, league games and the Champions League starting soon, we all need to be careful", Valverde added.
"It's always good when the best players get to play every game, but whether or not he plays will not influence the way we prepare for the game at all", Solari told a news conference on Tuesday.
Barca's insatiable captain equalised in the 64th with an unstoppable curling strike from outside the area, averting a first league loss for the league leaders since November and taking them on to 50 points from 22 games.
The Nou Camp club have already humbled Real once this season - stuffing them 5-1 back in October. "We are expecting them at their best".