The share price may have fallen to £8.21 on Monday after United floated on the US stock market earlier this month but billionaire investor George Soros has bought a 1.9% stake in the club, a US regulatory filing showed.
Since United's 10 August listing, the share price has fallen 6.7%.
United owners since 2005, the Glazers family raised £148m about half will go to pay off the club's debts, with the rest going to the Glazers.
Soros considered a takeover of Italian club AS Roma in 2008 but decided against it due to the club's debt problems.
The media right deals will attract investors to United.
"This could be a play by Soros on the strength of Manchester United's brand and the English Premier League's growing media rights," said Philip Hall, a partner at Inner Circle Sports, an investment bank focused on the sports industry.
"The domestic rights are set to increase 70% for the 2013-2014 season and the international media rights, set to be announced in late October or early November, are also expected to come in at a very robust uplift," he added.