Cape Town - Manchester United have reportedly tabled an opening offer of £21.5 million for Borussia Dortmund star defender Mats Hummels.
The Red Devils have sought to test Dortmund's resolve with a firm offer, according to German publication Bild.
In March, the Germany centre-back Hummels told German magazine Kicker that he "often thinks about moving abroad" and told German daily Bild a far stronger indication of his Manchester thoughts.