Michael Gault says Glentoran owe their fans a "massive performance" at Windsor Park or it will be "lights out" on their title dream.
The Glens trail Linfield by six points with just four games remaining this season, starting with a Friday's massive Big Two showdown in South Belfast.
Mick McDermott's side are still smarting from last Saturday's 4-0 drubbing by Crusaders, a result that has left their hopes of a first Gibson Cup since 2009 hanging by a thread.
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And former Linfield captain Gault accepts it is "all or nothing" for the Blues' bitter rivals.
"I think Glentoran owe their fans a massive performance, and there's no better place to do it than Windsor Park in a Big Two derby," Gault told Belfast Live's That's What I Call Football podcast.
"If I was David Healy I would be quite worried. Glentoran certainly weren't good against Crusaders, but I have been there before in games against Glentoran when they have been out of form and they turn up and beat you.
"And similarly when the Glens were doing well and Linfield were under-performing, we would end up beating them.
"There's a massive prize at the end of this here, and this is another game with three points on offer. But when you get there on Friday night and see the big crowd, the pressure ramps up.
"I am sure it will be a sell-out, and the Glens will want to get back in the title race. They have a good squad and will come out all guns blazing and it's all or nothing for them.
"Linfield won't want to lose or draw, but if they do, they can still win the league. If Glentoran lose then it's 100 per cent lights out for them.
"So the onus is on them to get a big result. But it won't be easy for the Glens. They have just been tanked by Crusaders and Linfield are flying."
Gault believes Friday night's derby showdown will reveal the true character of Glentoran's players.
From challenging for the Gibson Cup, the Glens have picked up just 14 points from a possible 27 in their last nine games.
"Back in the old days you had characters in the team, but will this Glentoran team give you a response like the Mark Glendinnings, the Paul Leemans and Colin Nixons?" Gault said.
"I know for a fact those old players would. These Glentoran players are very talented, so would I be surprised if they play out of their skins and win? No.
"But Linfield aren't going to lie down."
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