I can't say exactly what problem he has, I don't know.
"It's the same with Messi".
Madrid are seeking a 20th triumph in the competition, but it is their opponents who hold the upper hand as they have gone all the way a record 30 times, including four seasons in a row.
Ousmane Dembele, who also trained after recovering from two weeks out with an ankle sprain, has not been named in the squad.
Messi missed out on October's 5-1 win, a result that contributed to the sacking of Madrid coach Julen Lopetegui, and Valverde is enticed by the prospect of the clash.
Barcelona also have a higher average number of goals without him against their fierce rivals, than when he is on the pitch, albeit he has only been absent from three games. The Barca coach will then have to decide whether Messi is fit enough to start the game.
Messi did not take part in full training on Monday, but returned to join his team-mates on Tuesday for their final session.
A semi-final against Madrid adds to a complicated fixture list for Barca, but Valverde feels a busy schedule should not be used as an excuse for either side.
Barcelona host Real Madrid at the Camp Nou on Wednesday evening in the first of three El Clasicos in the gap of one month.
Asked at the prematch news conference in Madrid whether he wanted his fellow Argentine to be available for Wednesday's game, Solari said it would be best for the spectacle for Messi to feature. The next two will come back-to-back, with the second leg of the Copa del Rey scheduled for February 27 before a La Liga fixture on 2 March, both at the Santiago Bernabeu.
Real are the third most successful club, having won the trophy 19 times, although they last claimed the title in 2014.
Real Madrid: Improvement is what's on this team's mind, showing something better than in the first match of the season.