Arsenal, Manchester City and Manchester United all lost in the Champions League while Liverpool were held to a draw in France in the Europa League midweek.
West Ham boss Slaven Bilic revealed that he was not surprised by the results and underlined that Premier League sides must stop underestimating their opposition.
Bilic famously led Beşiktaş to a memorable win over the two legs against Liverpool in the Europa League Round of 32 last season but does not believe the result was a shock.
“For you it was probably a shock when Beşiktaş knocked out Liverpool last year. For us it wasn’t,” Bilic was quoted as saying by the BBC.
Bilic was Beşiktaş head coach for two-seasons and guided the Black Eagles to the Europa League quarter-finals last season.
The Croatian manager parted ways with the Istanbul giants to take over West Ham this summer and recently beat Liverpool again this time in the Premier League.
Beşiktaş are competing in the Europa League against this season and beat Albanian side Skanderbeu 1-0 in their opening group stage game.