Ousmane Dembele is unlikely to be fit to play for Barcelona in their first LaLiga Clasico of the season against Real Madrid, according to coach Ernesto Valverde.

The club's record signing, a €105million arrival from Borussia Dortmund to replace Neymar, will soon return to team training as he steps up his recovery from a damaged hamstring sustained in only his second league appearance for Barca.

A return for the Clasico against rivals Madrid on December 23 had been mooted for the France international, but Valverde played down Dembele's chances of being available for the crunch clash.

"I don't want to say it's impossible, but it looks difficult to me for him to be at the Clasico," Valverde told reporters on Tuesday.

"The injury has been serious, it takes a while and if we have to wait another week, we will wait.

"We are not here to take risks and we have to be sure. He's fine but we have to be cautious."

A draw at Valencia on Saturday maintained Barca's four-point lead at the summit of the table, but the match between the top two teams in the table was overshadowed by officials failing to spot an effort from Lionel Messi had clearly crossed the goal line.

LaLiga is set to introduce video replays for the 2018-19 season but Valverde believes technology should have already been adopted by the league, although he does not think either Barca or Madrid are unduly favoured by officials.

"From my position it wasn't possible to see if the ball had gone in," Valverde said. "I saw [Messi] celebrating.

"There were 40,000 people who saw it was a goal. It is absurd that the referee didn't see something so clear in a match as important as this one was. Every year there are incidents like this and they could turn out to be decisive.

"It seems absurd to me that we don't use technology. I guess that we'll have Hawk-Eye one day. Overall, the level is refereeing in Spain is good and it's difficult to referee. I wouldn't be one.

"Everyone has the right to complain. I don't see a difference between Barcelona, Real Madrid or other teams."

Barca host Real Murcia in the second leg of their Copa Del Rey tie on Wednesday, with Valverde set to give young players a chance to impress after his side's 3-0 first-leg victory.

"We've got the scoreboard in our favour and we're playing at home," Valverde said. "The idea is to repeat the first-leg performance by playing some of the players who don't get used as much.

"We have a limited number of youth-team places for the squad and Oriol Busquets is one of the options. We need to play good football and make sure people enjoy themselves."