Mariner told BBC Devon: "I said to the lads in the dressing room that there's a lot of twists and turns yet, even if there are only four games left.
"That's a lot of points at stake and there's a lot that can go on."
"We're sad but the lads are still fighting big time," he added.
Plymouth are away at fellow-strugglers Watford on Saturday, and Mariner knows a win at Vicarage Road is vital for their bid to stay up.
He said: "You've got to make your own luck, you've got to be forceful, you've got to be confident.
"This is no mug's league. You can see how narrow the margins are between success and failure, but we're still going to be battling next week."
Watford drew 1-1 at home with West Bromwich Albion on Monday to move four points clear of the Pilgrims at the bottom of the Championship table.
Source: BBC Sport
Source: BBC Sport