Chelsea winger Christian Atsu's proposed loan move to Vitesse Arnhem is being held up by complications surrounding his work permit, according to the Dutch club's spokeswoman Ester Bal.The 21-year-old moved to the Premier League from FC Porto this summer, but was immediately sent to the Eredivisie to continue his development with the opportunity for regular first-team football.Jose Mourinho has sent a number of promising Chelsea youngsters to Vitesse on season-long loan deals in 2013/14, but Atsu is the only player who is yet to gain clearance to make his debut."He is still waiting for a sticker and a stamp," Bal told De Gelderlander. "That will take a few days."As a result, the Ghana international has so far been unable to train with his new teammates, and remains doubtful for the weekend clash against PEC Zwolle.Vitesse coach Peter Bosz is looking forward to incorporating the Stamford Bridge starlet in his first-team plans, but must wait for the necessary paperwork to be processed before Atsu can be considered for selection.