Stuttgart's Argentine defender Emiliano Adriano Insua (L) and midfielder Christian Gentner (R) vie for the ball with Dortmund's Armenian midfielder Henrikh Mkhitaryan during the German first division Bundesliga football match between VfB Stuttgart and Borussia Dortmund in the Mercedes-Benz Arena in Stuttgart, southwestern Germany, on April 23, 2016. / AFP / THOMAS KIENZLE / RESTRICTIONS: DURING MATCH TIME: DFL RULES TO LIMIT THE ONLINE USAGE TO 15 PICTURES PER MATCH AND FORBID IMAGE SEQUENCES TO SIMULATE VIDEO. == RESTRICTED TO EDITORIAL USE == FOR FURTHER QUERIES PLEASE CONTACT DFL DIRECTLY AT + 49 69 650050 (Photo credit should read THOMAS KIENZLE/AFP/Getty Images)

Borussia Dortmund have again been rocked by the transfer window, now losing three of their best first teamers to other clubs, including their captain Mats Hummels to their biggest rivals Bayern Munchen.

The latest blow comes as Manchester United swipe talented midfielder Henrikh Mkhitaryan out from under them, which means they now have not one but two vital midfield spots to fill for next season.

Will BVB look within the club to replace the Armenian free kick specialist, or will they look to see what options they have on the open market?

Gonzalo Castro

Gonzalo Castro is almost certain to be starting for Dortmund next year. Where on the field though is the question. With the departures of Mkhitaryan and Ilkay Gundogan, Castro can fill in at either central midfield or right midfield depending on where he is required most. If no one new makes their way to the Westfalenstadion in the next few weeks, expect to see Castro somewhere in the lineup.

Karim Bellarabi

However, if the men from North Rhine do decide to make a move to immediately strengthen the first team, expect it to be right mid Karim Bellarabi from Bayern Leverkusen. Per The Daily Mirror, Borussia Dortmund has already made a bid for 26-year-old German, in anticipation for Mkhitaryan’s departure. Bellarabi is quicker than Mkhitaryan, which would obviously up the pace on the flanks, but is not quite the same level of footballer yet. However, it would hardly be a poor replacement option.

Juan Mata

Despite a reported chorus of disapproval from the Man United locker room, experienced Spanish midfielder Juan Mata is being linked with a move away from northwest England, with possible destinations being Everton, Spain and Turkey. While he does not fit within the usual mould of a BVB purchase, he would be a reliable and versatile stopgap option if Dortmund prefers to delay the development of their in-house options a few years. His resale would not be terribly high, nor has his form at Old Trafford been sparkling, but it would be a logical and safe move to make.