"He's been and gone. Mathias couldn't help the team, he is currently not in good physical shape," Uerdingen coach Stefan Kraemer told German daily Bild.
"Mathias has a good build for a 'Nine' (attacking midfielder) and is tall, but he is carrying too many kilos."
Uerdingen, a former Bundesliga club, earned promotion to the third division in May and won three of their four games this season, but turned down the chance to have a 'Pogba' in their squad.
Mathias, the 27-year-old brother of Manchester United and France star Paul, is currently out of contract having picked up an injury after spending the 2016-17 season at Dutch side Sparta Rotterdam.
He failed to win a contract after a trial with Uerdingen, who already have a World Cup winner on their books -- defender Kevin Grosskreutz, who was part of Germany's Brazil 2014-winning squad.
Mathias, who has played for British clubs Wrexham, Crewe Alexandra and Partick Thistle in a colourful career, cheered on his younger brother in Russia last month as France won the World Cup for the second time.
However, despite his famous surname and world champion sibling, the forward kept a low profile during his trial at Uerdingen, which is near Duesseldorf.
"Mathias did not let on that his brother is a World Cup winner," revealed Uerdingen's captain Mario Erb.
One of three brothers brought up in Paris, Mathias Pogba made the first of his five international appearances for Guinea in 2013.