Semenyo, 18, has made only one league appearance for the Robbins and is currently on loan at Newport County in League Two – where he has scored five times in 24 appearances.
But Tinnion claims United have been tracking him and that they might be interested in making a move in the near future.
“I was sat with a Man United scout at Newport the other week, to be honest,” he said.
“And they really like him. People will like him because he’s 18 years of age.
“We’ve got a lot of talent, there’s eight out on loan in the League at the minute and then probably 12 below the league.”
United have been linked with a host of stars who could come in and help them turnaround a difficult start to the season.
However, news of a move for a relative unknown might come as a surprise to the United fans.
They are currently eighth in the Premier League and have fallen eight points off the Champions League places after failing to win any of their last four league games.
While Semenyo is a striker, manager Jose Mourinho is said to see strengthening in defence as his top priority.
He had only one fit centre-back for the recent 2-2 draw with struggling Southampton at St Mary’s.
Mourinho has been linked with Harry Maguire from Leicester, Inter Milan’s Milan Skriniar and unsettled Tottenham star Toby Alderweireld.
Alderweireld is out of contract any the end of next season and a clause in his deal that means he will be available for a knockdown £24.5million becomes active at the end of the current campaign.
Spurs were demanding around £60m when United were interested in the summer but the two clubs could now come to a compromise so the Belgian, 29, can move to Old Trafford in January.
United are facing a huge rebuilding job next summer as a host of players are out of contract.
The club recently took up the option of extending David de Gea’s deal for one more year but he might need to be sold in the summer if they do not want to lose him on a free at the end of 2019/20.
Anthony Martial is in the final year of his contract but the club also retain the option of a one-year extension for the Frenchman.
Juan Mata, Ander Herrera, Phil Joes, Chris Smalling and Ashley Young are all out of contract at the end of this term.