The statistics you mentioned indicate that Brentford has won two and drawn one of their last three meetings against Chelsea, so for the past two seasons, Chelsea has struggled to defeat them. However, Chelsea is back on track as they were able to draw with Arsenal and win three Premier League games prior to the Arsenal game. Given that Brentford is not as strong as they were last season, they have a great chance of exacting their retribution on Brentford.
That could quite possibly happen to Chelsea because apart from having to take revenge by winning at home, Chelsea also have to continue fighting for full points in every match with a team that is not that strong. Because Chelsea still has plenty of opportunities to improve itself by continuing to win so that it can be in a better position than last season. Apart from that, Chelsea's own enthusiasm is still quite high after being able to draw with a strong team like Arsenal so Chelsea will try to get a chance to win at home when facing Brentford.