Real Madrid are closely following Borussia Dortmund’s Ilkay Gundogan and his back problems as they prepare a summer bid for the German midfielder. The Spanish giants have first refusal on the Borussia midfielder after they tried to sign him last summer, according to La Marca.googletag.cmd.push(function() { googletag.display(“div-gpt-ad-1389116196215-0”); });At the time Dortmund were reluctant to let Gundogan leave, given that they had just seen Mario Gotze sign for Bundesliga rivals Bayern Munich. However, the club’s made a pact and Madrid get first refusal on the 23-year-old. Gundogan has missed the majority of the season after sustaining a back injury back in August. Despite that there is still a clamour for his signature with Manchester United rivalling Madrid. The German international’s father and agent, Irfan Gundogan, suggested on Thursday that his future is open, further enticing suitors to test Dortmund’s resolve. With Robert Lewandowski also leaving for Bayern in the summer and Marco Reus interesting Arsenal and United, the loss of Gundogan as well would be tough to take for Dortmund coach Jurgen KloppRead more Manchester United transfer news.