Lionel Messi scored his first-ever goal against Chelsea in his ninth game against them as Barca came from behind to earn a 1-1 draw at Stamford Bridge ahead of the return leg at Camp Nou next month. Willian, who hit the post twice in the first half, opened the scoring for the hosts after the break with a well-taken finish from the edge of the area.

Valverde's team selection for the Champions League game was largely expected. Paulinho was included as the fourth midfielder with Philippe Coutinho cup-tied ahead of Dembele, who has just returned from a second hamstring injury.

Even when Barca went behind, though, Dembele remained seated on the bench, with Aleix Vidal brought on in place of Paulinho in the aftermath of Willian's opener.

"In a game of this calibre, after what we've gone through this season, I focus on what we have done up until now," Valverde said in his postgame news conference when asked about opting for Paulinho and then Vidal over Dembele.

"Behind the decision to play Paulinho is the fact it was not a game to experiment in, it is a game to be sure about. I had to respect what we have done until now, Paulinho is the third highest scorer in the team, then [with the substitution] what we looked for with Aleix Vidal was more width.

"[Dembele's] spent a lot of time injured and for a game of these characteristics coaches bet on things that they know and on things they have seen -- not on expectations."

Until Messi's goal, Barca had created very little. Paulinho headed wide in the first half and Luis Suarez flashed a shot across the face of goal in the second half. The equaliser eventually arrived from a Chelsea mistake and given the circumstances of the draw, Valverde admitted he was happy to be returning to Camp Nou with the advantage of an away goal.

"I see it very positively," he added when asked to assess the result. "It was a game of two different styles. We wanted to have control of the ball; they tried after the first few minutes to surprise us on the counter-attack.

"We lacked clarity in the final third but they defended well and there was a lot of traffic close to their area, so it was difficult for us. In the end, [our goal] came from an error from them and we took advantage of it. It's a good score given we were behind and clearly there is everything left to decide in the second leg.

"It is very important to have scored here and I am sure both teams will respect their styles in the second leg, too. They have the attacking resources to cause us problems [in Barcelona]. It's important to have go into that game in front with the away goal but this one is far from decided."

Defender Gerard Pique played with his knee strapped up for the second time and appeared to be struggling at times during the first half. Valverde admitted the defender is still not at 100 percent but played down concerns the problem is worse than the club have let on.

"Pique struggled a bit in the first half," the coach said. "But he ended the game better than we expected."