Valverde won't be sacked this 2018 unless Barça are out of the ChL, which seems unlikely.
The board and the team captains have expressed several times that the main objective this season is the ChL, La Liga being expendable other than the mandatory 2nd-4th spots.
I'm having a problem with the way priorities are set at Barcelona. Some clubs are different than others, and while Real Madrid usually don't win the league in the same season when they win the Champions League, we are the opposite. But it's more than just history and statistics - we've never managed to become champions of Europe without conquering our league and being considered the best team in Europe or at least in the top two or three teams, and I think that has to do with the style of play. Today, I wouldn't put us in the Top 5 and we're not winning the Champions League playing like this.
While we have names on the pitch that have already won and are more than capable of winning the Champions League, we don't have the manager to do it. Valverde is suited to the league format, as the boring grind week in and week out should bring us just enough points to beat anyone else even while playing awful football, because Messi. In the Champions League, it's much more difficult and you need to be mentally strong, tactically at least a little unpredictable and take advantage of your chances, all this while playing against the best teams. We can't win in that environment with this approach and I think this season will end badly if we decide to prioritize a competition that we are unlikely to win.
Pique said putting all of our eggs in the CL basket would be stupid and I agree with that. Let's not forget that no one really starts the season thinking "nevermind the league, the Champions League is our goal," instead clubs are forced into prioritizing the CL after they lose the domestic title race. Real Madrid didn't give up on La Liga and bet everything on the CL because they don't care about La Liga, they did it because they realized the league was out of reach halfway through the season.
I will not flatter Valverde by thinking we're doing the same as Madrid. The season's just started, we're simply playing poorly, end of.