"In fact, since that solid performance in Week One, the Jets’ defense has actually played better during the five games Johnson missed when he was injured. Many league observers believe Darryl Roberts, the minimum-salary backup who was starting while Johnson was hurt, has actually played better than Johnson this season. That’s despite the fact that Johnson will pocket $26 million in salary and bonuses in his first year with the Jets, while Roberts makes less than $1 million."
You can find evidence that he wasn't "fine" all over. Not sure why you believe he was ok.