The Blues face a potentially tricky clash against top-four chasing Southampton at Stamford Bridge fresh from their Champions League last-16 exit on Wednesday night.
However, former Arsenal midfielder Merson doesn’t anticipate Jose Mourinho’s side suffering from a European hangover despite a subdued performance against PSG.
Merson told Sky Sports: “I think Chelsea will bounce back from the PSG game. It’s a tough game for Southampton, who have done great this season.
“Diego Costa is definitely due a goal – he hasn’t scored in seven games. He didn’t score a single goal in the Champions League. That is unbelievable as it wasn’t the hardest group in the world.”
Chelsea are five points clear at the top of the Premier League having played a game less than Manchester City, who failed to close the gap earlier this month after a 2-1 defeat by Liverpool at Anfield.
Meanwhile, third-placed Arsenal welcome London rivals West Ham United to Upton Park on Saturday afternoon, and Merson backed Olivier Giroud to return to the starting line-up and to score against the Hammers.
“West Ham have hit a bit of a bad run and this time of year, Arsenal are very reliable,” Merson added.
“It was good to see Danny Welbeck score for Arsenal at Manchester United but I think they’ll play Olivier Giroud in this game and he can score first in a 3-0 win.”
Arsenal were 2-1 winners against Sam Allardyce’s side at Upton Park in the Premier League earlier this season.
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