A win to Thistle would take them two points above United, with the game in hand still to play.
Third-placed Taradale, two points behind Thistle, do not play tomorrow.
Gisborne United player-coach Corey Adams says tomorrow’s match is “a massive game that could decide the league”.
“It’ll be a tough match and it could go either way,” he said.
The Challenge Cup — held by United for over a year and at stake for every home game of the holders — will also be at stake.
“It’s not often you see two Gisborne sides battling it out at the top of the league and that’s great to see for football here,” Adams said.
“Gaz (Thistle coach Garrett Blair) has a good squad with a lot of depth and it’s going to be a very hard game for both sides.”
United will be without central midfielder Dane Thompson, who has a knee injury, but the rest of their squad should be available.
Thistle coach Blair said he was pleased with the way his squad trained this week.
He was relieved they were able to get back on the field last weekend and build up some match fitness, in the lead-up to this game.
Blair is disappointed with the way the League has been revised, with Hastings Hibernian dropping out of the division.
The decision was made to give every side a 3-0 default win against Hibernian. That cost Thistle nine goals in their goal difference, which could be critical at the end of the season.
“We and United appear to be the form teams in the league,” Blair said.
“It sets up this weekend to be a cracker.”
Thistle won the first-round game at Childers Road Reserve 4-1.
“This is a different United team and they will be up for it,” Blair said.
He welcomes back to his squad first-round man of the match Matt McVey.
With so much depth in his squad and everybody raring to go, Blair had not decided on a starting line-up last night.
But he knows his team are fit, strong and ready.
Blair believes in possession-based football and expects his side to keep the ball and use it wisely.
United won the corresponding fixture last year 2-1.
