Barca's Lionel Messi 'spectacular to watch' - Ernesto Valverde

BARCELONA -- Lionel Messi is "spectacular" to watch says Barcelona boss Ernesto Valverde, who hailed the Argentine's decisive setup in his side's Copa del Rey win on Thursday.

Messi was once again the catalyst for Barcelona as they battled to a 1-0 win over Valencia to take a slender lead into next week's Copa semifinal second leg.

Barca dominated the first half, completing 438 passes in just 45 minutes, but failed to trouble visiting goalkeeper Jaume Domenech.

However, they continued to probe after the break and eventually broke through in the 67th minute when Messi created something out of nothing for Luis Suarez to head home.

Receiving the ball in the area, the Argentine twisted and turned his way to the byline before standing the ball up at the far post.

"What happens with Messi is that every time he gets the ball, you expect him to do something," Barca coach Ernesto Valverde said in his postgame news conference.

"Sometimes that's excessive because you have to let him breathe a bit, but it's spectacular to watch him. From an improbable situation, he's dug out a cross and we've scored."

Despite winning the game, Barca may regret not scoring more goals, although Valverde was happy not to concede an away goal.

"As much as we wanted to attack well, we didn't want to allow any counter-attacks," Valverde added. "Valencia are dangerous in that regard and that's what they were looking for.

"They defended well, kept their two lines of four together and left very little space through the middle. There was more space out wide and we could have solved things earlier with better luck from one of our crosses.

"We would have liked to have scored more goals but it's still a good scoreline because we won -- and because Valencia did not score. We will try to defend our advantage there next week."

Suarez said he believed there is still plenty of life left in the tie.

"It's a minimal advantage that we have because there are 90 minutes left,'' Suarez said in quotes reported by Marca.

"Valencia at home are always stronger and even more so in a Copa semifinal.''

Barca have not had a midweek off since the turn of the year and that won't change next week, with the second leg at Mestalla pencilled in for Thursday.

Before then, they travel across Barcelona for a Catalan derby against Espanyol in La Liga on Sunday, with Valverde confirming there will be changes due to the fatigue which is building up in his squad.

"The accumulation of games is a worry that all managers have," Valverde said. "But that's how it is. It's the price you pay for continuing in the competitions you want to win, a consequence of playing well in all three competitions.

"We have played a lot of games this month. You notice [the fatigue] as the time passes. There's hardly any space between one game and the next. Now, it's nearly Friday, and we have a game on Sunday, an important game, a derby, so there will be some changes."

One player who may not need a rest is defender Samuel Umtiti, who looked as fit as ever in an impressive performance against Valencia after returning from a hamstring problem two weeks ago.

"Umtiti was in great form when got injured," Valverde said of the France international. "Now he's back and you can see that with the rhythm of games he's getting back to that same level again.

"He's very important for us. We are a team that plays with a lot of space left behind, so to have a player with so much pace and able to cover is really good for us. We're happy not just because he's back, but because he's back at a great level."