The Blues rather surprisingly took the decision to part with a two-time Premier League title winner in 2017, with Antonio Conte opting to freeze the Spain international out of his plans.
In the wake of his return to Atletico Madrid, those at Stamford Bridge have struggled to build on their past successes – with Alvaro Morata struggling to fill some big boots.
Arsenal, meanwhile, have also regressed and will be charged with the task of trying to contain former domestic foe Costa in a Europa League semi-final second leg clash on Thursday.
Lampard believes the Gunners are crying out for a Costa type, and that Chelsea are not the same without him, telling the Evening Standard: “Arsenal’s task of beating Atletico Madrid was already tough, but it’s a lot harder with Diego Costa now up against them.
“Costa is exactly the kind of personality missing from Arsenal’s dressing room, someone with that winning mentality.
“The English game has missed him this season after he rejoined Atletico from Chelsea.
“He is a big player, a big character. Love him or hate him, you have to appreciate that kind of player.
“Chelsea have certainly not looked the same without Costa. Not only is he a big physical presence, he has great quality to score goals.
“That is why I fear for Arsenal on Thursday night in the second leg of their Europa League semi-final.
“Of course they’re still very much in it at 1-1. But they failed to defend properly against Antoine Griezmann for Atletico’s goal in the first match and now Costa, who was an unused substitute after just coming back from injury, will face them too.”
Costa scored three goals in six meetings with Arsenal during his time in England and will be hoping to enhance that record at Wanda Metropolitano in midweek.