Arismendi, signed earlier this month on loan from Stoke until the end of the season, has made an instant impression at the Galpharm Stadium.
Grayson said: "It's something we've wanted to do, to take it to the next level. No disrespect to the other lads who have been playing in midfield, Diego has come from a Premier League club and his main strength is his composure.
"A lot of the other midfield players we have at the club have a lot of other qualities that you need throughout the course of the season, but Diego has that composure and he will get better.
"He's composed when he's got the ball, he has a physical presence as well and he will get better the more games he's involved in.
"He's not played a lot of football, but full credit to him. He's settled in really well, the group have taken to him and hopefully he can produce a few more performances like the one against Charlton."