The 28-year-old arrives with a wealth of experience under his belt courtesy of nearly 400 senior appearances at a number of different clubs and under lots of well-known managers.
But what have those former managers said about him at various stages of his career?
Here are the summations of four bosses well-known in South Yorkshire circles, all of whom know Vaulks better than most.
Released by Moore at Tranmere Rovers when he was just 18, Vaulks had to do it the hard way, battling back from non-league football at Workington Town before heading north to Scotland.
Five-foot-nine Vaulks was too slight to pay at centre-half for Moore, it was felt.
“Will wants to play regular first team football and, unfortunately, there are others ahead of him at Tranmere,” said Moore on his release from the club.
“It's better for his progress to play competitive football regularly for Workington than for our reserves so this is a good move for him.
“He's a good lad, has a great attitude and I wish him the best of luck for his future.”
After a move to Scottish side Falkirk and a successful three-year stint at Rotherham United, Vaulks made the switch to Cardiff City in what was an undisclosed record sale for the Millers. There he joined former Blades boss Neil Warnock.
“He's right up my street,” Warnock said.
“(Rotherham manager) Paul Warne worked under me at Rotherham and said I should take a look at him. He can play in front of the back four but he can also get into the box and get a few goals. He's a good lad and I think I can get a bit more out of him.
“I think he could do better in this side with the players we've got around him and I'm looking forward to seeing what he can do.”
Time moved on and Warnock’s fellow South Yorkshireman McCarthy took the reins in South Wales, where Vaulks had taken a little stick from some sections of the fanbase as results soured.
“The lads have been great with their pressing and their organisation and Will was a big part of that,” he said after a 4-0 win over Derby.
“They went and nicked it again, time and time again. I think Will is brilliant. I think he was much-maligned at times but he doesn’t half put a shift in and it’s obviously great to see him get a goal.”
His old Millers boss is one of his biggest fans and said earlier this summer: “I obviously love Will, so if I could get anywhere near Will's wage demands that would be a player I like. However, I do not expect Will to sign this summer is probably my nicest answer.
“I did speak to him but it isn't like 'Oh what's happening this summer'. I have spoken to him loads of times and he has phoned me for advice while he's been at Cardiff which I have given.”