Mohsni returned to the club for the first time since last May, when he had expressed his desire to leave, to line up at centre-back.
But he was dismissed for the fifth time in his Southend career for a terrible challenge on Cobblers winger Chris Hackett after just 27 minutes. Yet Sturrock still claimed he was right to hand the Frenchman a recall.
"I don't regret bringing Bilel back in because it was the right thing to do with the players we have unavailable here at the moment," said Sturrock.
"I don't think we can have any complaints about the red card but I don't think it was a malicious tackle at all.
"He just mistimed it and caught their player instead of the ball so I feel for him.
"I will talk to him about the situation on Monday but it's too early to say if he will ever play for us again and those questions shouldn't be asked at this stage."
Before Mohsni's red card, Northampton had taken the lead in the 11th minute when a long throw from Ben Tozer on the right was flicked on to the far post where former Shrimpers loanee Roy O'Donovan hooked home.
But the Cobblers were unable to hang on to the lead and, in the 65th minute, Southend's Matthew Lund, who was making his debut after signing on loan from Stoke, headed a home a right-wing corner from Kevan Hurst.
However, Northampton survived some scares and stole it right at the death when captain Kelvin Langmead headed home from close range in the 90th minute.