The former Saints forward believes manager Mauricio Pochettino needs to add to his squad this summer and partner the prolific Aston Villa man with Rickie Lambert up front
Mauricio Pochettino has so far signed £8.5m Croatian centre-back Dejan Lovren from French club Lyon, with the likes of Victor Wanyama and Cagliari’s Radja Nainggolan also linked to the club.
But Watson believes that as many as five quality players are needed if Southampton want to think about challenging for European qualification, and thinks they should go all out for Bent.
"Saints need to sign five more quality players," Watson told the Daily Echo. "We need to sign a first-team striker to play alongside Rickie.
"If you are serious about trying to get into Europe, you need at least three players in double figures. But last season we only had one.
"We need a natural goalscorer, someone like Darren Bent would be ideal. People might say he would cost too much, but I would say how much could it cost if you didn’t get a player like him?"
Lambert was on of Southampton's success stories last year and Watson was quick to praise him, though there are certain players he believes Pochettino needs to get more out of.
"Rickie did very well [last season]," he added.
"To finish as the joint top English scorer, you could not have asked for any more in his first Premier League season.
"He’s been on an upward curve ever since he joined Saints, but how many goals did he score towards the end of the season?
"Was he tired, was he burned out after a tough season? Or was the way he was being asked to play by Pochettino, not so far advanced, play a part?
"[Southampton] have brought in one, but they need a lot more if they want to take it to the next level.
"I would say they need two more top drawer centre-backs because ideally you’d want four of them to pick from.
"We haven’t seen the new signing [Lovren] yet and we haven’t seen what [Vegard] Forren can do either.
"Jos Hooiveld and Jose Fonte are ok Premier League players, no more. And the jury is still out on Maya Yoshida because of his positioning.
"He likes to play behind the line and if other clubs capitalise on that it could be a massive problem for us. He wasn’t a positive for me [last year]."