Ian Ross, who has been at the Pilgrims on loan for one month has impressed the York Street crowed which has prompted the club to extend his loan spell.
He was however due to return to Bramall Lane this week, but has been signed up in time to play for the League Two side at Darlington which is played tonight.
"It is great news to have Ian on board for another month," said United manager Steve Evans.
"He's done well during his first month with us and I'm looking for him to continue what he's been doing."
Meanwhile youngster Simon Francis has netted a loan deal with League Two leaders Grimsby Town, the Mariners who recorded that famous 1-0 win over Tottenham Hotspur last week has landed the former Bradford City trainee for one month.
Francis (aged 20) has suffered some injury set backs since his transfer from the Bantams in March 2004 but the Mariners have won the race to sign this promising Defender.
"Simon is a player that needs games and this will benefit him," Blades boss Neil Warnock told sufc.co.uk.