United have had a couple of academy prospects on the warm weather training camp in Spain - including one who enjoyed his 18th birthday on the trip.
Striker Oliver Greaves and goalkeeper Marcus Dewhurst, who celebrated his birthday on Wednesday, are part of the Blades contingent.
Marcus said: "I've had fun so far, it's been enjoyable being around the lads, it's a privilege to be called up, not everyone gets the chance.
"It is a lot different to academy football, the tempo is a lot higher and you cannot afford to lose your head."
Oliver added: "I think it is a lot different, a lot quicker, hopefully I'm doing well.
"The senior lads have been good, we are divided at Shirecliffe but it is good here. I'm a bit more nervous being with the senior lads but when you get over the line onto the training field, the difference is that it is just a bit quicker."
Marcus has been capped at England junior level and has spent time on loan with Gainsborough Trinity and Guiseley, whilst Oliver is a versatile forward, who has captained the U23s on several occasions this term.