The defending Premier League champions ended a three-game winless run with a 4-2 victory over Watford at Stamford Bridge last weekend.
The Blues lost 1-0 to Manchester City at Stamford Bridge in their final Premier League game before the international break.
Chelsea suffered a surprise 2-1 defeat at the hands of the Premier League’s basement club Crystal Palace at Selhurst Park earlier this month.
Antonio Conte’s side had to come from behind to rescue a 3-3 draw with Serie A side AS Roma in the Champions League group stage.
Chelsea won the Premier League title with two games to spare last season after finishing seven points clear of Tottenham Hotspur.
The Blues are already nine points adrift of leaders Manchester City in the Premier League title race.
Former Chelsea midfielder Nevin believes the defending champions are lacking zip at Stamford Bridge.
“Chelsea aren’t playing that well. They aren’t that zippy,” Nevin told BBC Radio 5 Live.
“They don’t look that fresh. They look like a tired group.”
Chelsea won the Premier League title in two of the past three seasons.
The Blues signed six players in the summer transfer window to improve their squad ahead of a return to the Champions League.
The west London side lost 2-1 to Arsenal in the FA Cup final at Wembley.
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