The probability that Arsenal loses tomorrow's game against Brentford is quite minimal. If they lose yet another game, it will be clear that they are not prepared to hold the title of Premier League Champions for this year. They are aware of what would be at risk for them if they lost against Brentford. They won't be as fortunate this time around as they were last week to see Manchester City lose their match as they did to Everton. They will get to see how Manchester City will overpower them to lift the PL title again if they lose other of their matches by mistake.
Arsenal will not lose to the Brentford team, Arsenal will provide resistance and it is likely that they will take advantage of the opportunity in this match to score lots of goals in order to get additional points that can make them even further away from the second position from the top of the standings so that Arsenal will remain safe in first place until the end of this league.