Hendon saw his side briefly top League Two at the start of September but has been unhappy with two straight draws which have left them in fourth - one place below the Millers.
He said: "This football club has been mediocre for too long.
"I've set my standards higher and I know where I want to be at the end of the season, and the lads do too.
"I know where this team can be and that's what I'm striving for. The last two performances are not going to get us where we want to be."