Mourinho accepted responsibility for his side's shock 2-1 defeat to Basel in their opening match of the Champions League - their first home defeat in the group stage for 10 years.
Mourinho still expects Chelsea to advance to the knockout stages - they travel to Steaua Bucharest next - but Redknapp told Sky Sports the Portuguese must settle on a first-choice line-up and formation to achieve that goal.
"If it wasn't Jose Mourinho, you'd probably be thinking 'what is this guy up to? What's their best system? What's their identity? How do they play?'" Redknapp said.
"I've seen him use so many players in different positions since the start of the season. I still can't believe he's not picking Juan Mata. When I think about Chelsea retaining the ball and people who are comfortable on it, Mata has to play.
"I just think at the moment there's no real system to the way that they play. Where's Andre Schurrle? Where's Kevin De Bruyne? I don't think Jose really knows what his best team is.
"When you play football, it's about building relationships - be it centre-backs, midfielders, wide men, front men. At the moment, no-one seems to have any relationship with anyone because they don't know who he is going to play."
Oscar gave Chelsea the lead just before half-time at Stamford Bridge only for Mohamed Salah and Marco Streller to earn the Swiss side victory.
Redknapp believes that a lack of firepower up front was undermining Chelsea's start to the season, comparing the current squad to the one that won back-to-back Premier League titles under Mourinho in 2004-05 and 2005-06.
"Mourinho built his success at Chelsea on Didier Drogba - he was the focal point of the team," Redknapp said. "But Samuel Eto'o floats out to the left, he floats out to the right. That gives you no-one to play off.
"I know what Drogba did is history but I still believe you need someone up there. They've got so many players who keep wanting to come inside that I don't see any width.
"No-one wants to run without the ball - everybody wants the ball to feet. I couldn't believe the performance that Eden Hazard put in. He should be lighting the place up.
"I thought he'd be really flourishing under Jose but he was so disappointing. I didn't see him go past the full-back once."