The WTA tour is wide open with no real dominant force for the first time in two decades.
Williams and sister Venus have lost their grip on the women’s game as they reach the latter stage of their careers.
Serena is hoping to equal Margaret Court’s all-time Grand Slam record of 24 titles by winning the US Open later this month.
But seven-time major winner Wilander thinks she no longer holds the advantage over her peers.
“Her intimidation factor is slowly disappearing, compared to the youngest ones,” Wilander told Eurosport.
“She has not been consistent in the last four or five years on the regular tour and has not played enough tournaments and won enough victories.
“The dressing room probably thinks that there is a small chance that they can win because the consistency – both physical and in their tennis – has not been there.
“The intimidation factor is not as strong with Serena, as it is with someone like Roger or Rafa.”
Meanwhile, Wilander also discussed the attention Nick Kyrgios will receive at the US Open.
The Australian was slapped with a £93,000 fine at the Cincinnati Masters last week for five offences which included a verbal assault of umpire Fergus Murphy.
“I hope he doesn’t behave like he did in Cincinnati,” Wilander said.
“I think that every week that passes is showing more and more interest in wanting to win tennis matches and wanting to improve everything around him.
“Well, maybe not his behaviour on the court.
“But I don’t care, I think when he did what he did in Cincinnati, of course it looks bad and, of course, there are children in the stands and the language is bad, but at least the way he is now in the last weeks, he is showing that he cares.
“Nick wants to win, he hates losing and he wants to play well, he wants to entertain and he simply hasn’t been able to deal with it in a professional way.”