Crewe manager Dario Gradi has made signing a new defender his top priority before the end of the transfer window.
Teenager Harry Davis made his first start for the Alex in the 3-0 defeat at Swindon on Saturday, while 17-year-old George Ray was named as a substitute.
Gradi told BBC Radio Stoke: "Before the month is out, we'll sign somebody because we need the cover.
"Either that or George will impress enough but I'm loathe to have to rely on him, talented boy though he is."
Gradi did not add an outfield player to his squad during pre-season, with Scotland Under-21 goalkeeper Alan Martin his only recruit on a free transfer.
Nine of the 11 players that started at Swindon were products of the club's academy.
BBC Radio Stoke will have live commentary of Preston v Crewe on 1503MW and DAB digital radio from 1945 BST on Tuesday, 9 August.