Former Tottenham striker and BBC Sport pundit Garth Crooks has described Chelsea's decision to let midfielder Willian join London rivals Arsenal as madness.
The Brazilian winger made his Arsenal debut on Saturday and, during a commanding Craven Cottage performance, provided a brace of assists for his team-mates and played a key part in the third as they romped to a 3-0 win.
Alex Lacazette, Pierre-Emerick Aubameyang and new-boy Gabriel were all on the scoresheet on what proved to be a perfect day for Mikel Arteta.
And he will have been delighted with his new arrival, says Crooks, while Lampard watched through his fingers having let the star depart in a move that could cost him dearly.
"I said last season that Chelsea could not afford to lose him," Crooks said, speaking to BBC Sport.
"To let him go to London rivals Arsenal, of all teams, was madness and could cost them dearly in the final analysis.
"Against a Fulham side who were out of their depth, Willian produced a debut performance that must have been an agonising watch for his former manager Frank Lampard.
"The Brazilian was merely finding his bearings with a free-kick that flew past Fulham keeper Marek Rodak and hit the post."
He added: "He left Craven Cottage with two assists under his belt, and a 3-0 victory."
