Keita struck from the edge of the box to break the deadlock and put RB Leipzig in front.
The ball took a wicked deflection and sailed beyond the Schalke stopper.
Liverpool are locked in talks with the German side as they look to secure Keita this month.
Liverpool have a deal in place to sign Keita in the summer but want him earlier after selling Philippe Coutinho to Barcelona.
But Leipzig boss Ralph Rangnick claims he’s staying put until the end of the season.
“[Naby Keita] wants to leave us in the summer,” he said.
“He will play with us until the end of the season. He is starting today. There isn’t more to say.”
But his goal was branded a leaving gift by fans on Twitter.
“Leaving gift,” Harry Purdie said.
Sean Girling posted: “Great parting gift.”
Elvis said: “Scoring on his last game, very nice NK8!”
Talks remain ongoing over the deal but it appears closer than earlier in the week.
Yesterday Keita registered a company in the UK amid claims the deal would be complete by Sunday and he would wave goodbye to Leipzig fans this weekend.
A company under the name ‘NK8 LIMITED’ has been registered on the Companies House website. Two people are listed as officers – Naby Deco Keita and Bjorn Alexander Bezemer.
Bundesliga journalist Chris Williams then tweeted: “Information from within Leipzig this evening that Naby Keita will become a Liverpool player on Sunday.”