Halford became the seventh summer signing when he penned a two-year contract on Monday and his capture has caused waves of excitement in the Millers camp.
Not only does he have vast experience of playing in the Championship - a division the Millers are still trying to crack - but he also has the ability to play four different positions.
Rotherham had to work hard to get the 30-year-old through the door, meeting the former Forest man on four separate occasions, but his ability to play in so many areas of the pitch made it worthwhile.
"The nice thing about Greg is that we have seen him play right-back, centre back, centre midfield and as a striker and he is competent and indeed excels in those positions in the Championship," Raynor said.
"That is why he was so highly sought after. The nice thing with Greg is a lot of players put themselves in a pigeon-hole and say, 'I am a central midfielder or a striker or whatever'.
"With Greg, we asked him where he sees himself - and we have a fair idea of where he will fit in - and after saying, 'Where do you want to play?' he said, 'I don't mind'.
"He will do whatever to help the team and that's the type of a character we will need with a smaller squad than the so-called bigger clubs."
Halford is not the only play who can operate in several positions, with Frazer Richardson, Kirk Broadfoot, Tom Thorpe, Danny Ward, Lewis Buxton, Aidy White and Emmanuel Ledesma all capable of moving around the pitch.
And Raynor believes that leaves the Millers in a strong position.
"We'll need that versatility and Lewis Buxton can play centre-half and Aidy White can play left-back or left midfield, Danny Ward can play wide or up top, Ledesma can play just off the top," he added.
"Versatility is going to be absolutely vital for us and just the answer we needed from Greg.
"We will see what pre-season brings and look at a number of options and formations and positional changes with players and see where it fits in with what we are trying to do.
"We're excited about it. Training has been good, we haven't done a lot with the footballs, but what we have seen has been fantastic."
