The 27-year-old signed for £10million in the summer and promptly scored on his debut against Stoke on the opening day of the season.
Since then things have not gone so smoothly for the Swedish international and, with a return of just five goals from 25 Premier League starts, many people have already labelled the striker a flop.
Furthermore the former Toulouse ace has not scored since 13th December, a run stretching 12 games, prompting fans to call for him to be dropped.
The dissenting voices got louder on Saturday when, after the frontman was replaced with the Trotters 4-0 down against Chelsea, they fought back to 4-3.
"Johan is getting criticised and he didn't play particularly well against Chelsea," Megson told the Manchester Evening News.
"But he will be playing against Portsmouth and, like everybody else, he will be judged on how he plays.
"Johan has got a great work rate and great movement and that contributes to the fact that Kevin Davies and Matty Taylor, who play alongside him, have scored 10 and 12 goals.
"It's a team thing but he needs to start chipping in with more goals.
"Johan knows that and he's disappointed, but he does work hard and is a talented player.
"His game needs to adapt a little bit more to English football because it's much more physical over here.
"He had a period when he got four goals in a few games. If he did that again and ended up with nine goals, would that mean he'd had a fantastic season?
"I've looked at other centre-forwards, how much they cost and their goal ratio. Johan is by no stretch near the bottom."
Portsmouth v Bolton 1st Goalscorer: Elmander, J. 15/2