Bielefeld secured a vital 2-0 over their higher placed Bochum at the Schüco-Arenaat the weekend.
The win sees Arminia, who are fourth from the bottom open up a four point gap over Nürnberg, who could only draw with Dortmund on Saturday night.
Coach Michael Frontzeck –who has openly expressed his desire to keep Fernandez between the poles and not change a winning combination - had to wait until the 70th minute to see his side take the lead with Mijatovic heading in a Kamper free kick from close range.
The vital three points were sealed late on in the 90th minute when winger Jonas Kamper took advantage of plenty of room in the Bochum back line to fire in a right footed shot on his birthday to seal the win.
All eyes will be on Fernandez on Tuesday when Arminia take on table topping Bayern Munich.
Bafana Bafana winger Sibusiso Zuma did not have much game time as he was only brought on as a substitute for Christian Eigler in the 84th minute.