Portsmouth Ladies captain Charley Wilson says her side "should not be afraid" of Sheffield FC on Sunday.
The winner will be promoted to Women's Super League Two, subject to a licence.
"I think we can do it," Wilson told BBC Radio Solent. "It's a one off game and anything can happen. I think we've got the strength in the squad to do it.
"Sheffield are a good team, they're a bit similar to us and quite a physical side."
Portsmouth lost 2-0 to Sheffield when the teams met earlier in the season in the Women's Premier League Cup.
"On that day we didn't play very well," Wilson added. "I think we were a bit afraid of them. This time around, we know what they're about, and we should not be afraid.
"Maybe it's a good thing that they've played us because they might be a little overconfident."
|Comparative league records this season|
First team manager Perry Northeast added: "Both teams will go in there flying with confidence. We'll have a plan and want to execute it properly.
"Sheffield are a really good side. They are a bit like us. When we played them (earlier in the season) I felt we didn't turn up.
"If we just up our game by five or 10 %, who knows what can happen."
Sunday's play-off game kicks off at 14:00 BST at the chosen neutral venue, Stratford Town FC.