Coates will be in the Belles dugout for the last time when struggling Aston Villa visit the Keepmoat Stadium in FAWSL2 on Sunday.
She is leaving the club to take up a specialist coaching role with England Women’s U18-U20 sides just over a year after being appointed head coach.
Belles followed up victory at London Bees with draws against Oxford United and Millwall Lionesses.
Ahead of her final match, Coates said: “We’re undefeated in the league and we’re disappointed not to have taken all three points from each game.
“For me moving forward now it’s about leaving the club in the best possible position after the next league game.”
Current assistant manager Kate Rowson will take interim charge of the Belles from November 1 as the club search for a new head coach.
After winning their opening match in London they surrendered leads late on against Oxford and Millwall - and sit seventh in the early standings.
They lost 3-0 in the FAWSL Continental Cup against top flight side Everton last time out.
Despite the slow start, young striker Chloe Peplow is still confident her side can challenge at the top of the FAWSL2 table.
Peplow joined the club on a three-month loan deal from Birmingham City but has missed the last two weeks with an ankle injury.
She said: “We got the result we wanted in the first game and then we were ahead until 80 minutes in the last two before conceding late on.
“The team’s been quite disappointed with the results because we know we should be high up in the league. We’re looking to put that right now.
“Doncaster are one of the teams that should be trying to go top of the league, so now we’re looking to progress and get the league results to try and do that.”
Villa have so far lost three out of three in the league.