Louis van Gaal is weighing up three replacements for the injured Luke Shaw as he looks to rebuild Manchester United's left flank after the "big loss" of seeing the full-back ruled out for most of the season.
Shaw will be sidelined for six months after suffering a double leg break in United's 2-1 defeat to PSV Eindhoven on Tuesday.
Van Gaal marvelled at the mental strength of the 20-year-old and is debating whether to ask Daley Blind, Marcos Rojo or Ashley Young to take over from the England international.
But, after voicing his belief Shaw would have a superb year and establishing a youthful partnership between the left-back and Memphis Depay on that side of his team, Van Gaal admitted he has work to do to form a new alliance.
"It is for us a big loss," he said in a news conference. "I said in advance it shall be the season of Luke Shaw and now it is finished nearly. He started so well.
"We built up a left wing with Memphis Depay and Luke Shaw and we have to start building again. That is not so easy but we have to do it."
Blind started the season as a regular in the centre of United's defence but was shifted to left-back in Eindhoven when Shaw was stretchered off and Rojo came on to replace him. Young, who was more accustomed to operating as a winger, played in defence at times for Van Gaal last season.
"Shaw is the line-up player," the Dutchman said. "It is very difficult to replace him. Certainly when he is in such a good shape. We have good replacements in Blind and in Rojo and in Ashley Young."
Shaw remains in the Netherlands after undergoing surgery and Van Gaal said United will do whatever they can to make life easier for him when he returns to England and as he tries to regain fitness.
"I called him last evening [Thursday] so he sounds very strong," he said. "It was amazing for me, a big surprise and a good signal but he knows it is a long way he has to go.
"It is not easy but his family is there. We sent people to him. When he can come back, we have everything prepared. Maybe he can come back [to England] tomorrow [Saturday] and then he will have a long period of rehabilitation so he has a long way to go.
"I am always saying about the total human being principle. It is not only physical but mental."