The 32-year-old Brazilian Gunners joined the Gunners on a free transfer in August after his contract with the Blues expired.
However, he admitted in an interview with UOL earlier this week that his preference was to remain at Stamford Bridge, saying: “Everyone knew the conditions, I really wanted to stay.”
And speaking on commentary duties for BT Sport for the game, Keown appeared far from impressed with Willian’s comments.
“Well, I saw in the week about him saying he wanted to stay at Chelsea,” he said. “Is he a player almost in mourning because he’s missing Chelsea?
“He’s now an Arsenal player, he’s got to give his best for the football club, they’ve rewarded him with a three-year contract but he hasn’t really performed.
“It’s almost not being in the mood, he’s looked glum as a player so he’s got to play his way in now.
“There’s been some minutes on the pitch, let’s see what he can do. He’s always been a player I admired at Chelsea but I’ve not seen the same in an Arsenal shirt.”
Willian did go some way to silencing his critics, however, by setting up Arsenal’s equalising goal against the Foxes as his free-kick was met by a David Luiz header after Youri Tielemans had put the home team ahead.
And he also played a big part in the goal which gave the Gunners the lead, with his searing pace down the wing ultimately leading to a Nicolas Pepe cross which Wilfried Ndidi handballed in the box, with Alexandre Lacazette converting the resulting penalty.