They host London Scottish, who are uncatchable one place above them in third and, ahead of the semi-final first legs next weekend, seeking to regain some form after a heavy loss at Yorkshire Carnegie.
Neither know yet who their opponents will be; leaders Bristol head to second-placed Worcester Warriors this afternoon to decide who takes first spot and secures that two-legged semi-final with the South Yorkshire club, with the other side facing Scottish.
Rotherham won 21-10 at Nottingham last week to end their opponents’ hopes of clinching fourth spot and Blackett said: “I was really pleased with how the boys played; I thought they put in a real clinical performance and I think the experience we gained from playing in these big games last season really helped us.
“We feel we are in good form at this moment in time and if we are going to get to the play-offs (there is still a mathematical, albeit unlikely chance Rotherham can be pipped for fourth) we want to make sure we’ve got as much momentum as possible.
“But to get the win against Scottish is not going to be easy.”
Doncaster Knights make the long trip south to Plymouth with their relegation fears long since eased.
Director of rugby Clive Griffiths makes a handful of changes to the side that defeated Bedford Blues last week.
Paul Roberts replaces Ume Fosita at fly-half as he makes his first return to his former club while there is a complete overhaul of the front-row with Richard List, Ben Hunter and Colin Quigley taking over from Tom Davies, Harry Thacker and WillGriff John.
Plymouth were relegated after last week’s 29-0 defeat at Moseley confirmed demotion to National League One.
Carnegie chief Bryan Redpath is forced into two changes for their home game with Cornish Pirates who have yet to win in six trips to Headingley. Ex-Pirate David Doherty and Chris Pilgrim are both ruled out with injuries meaning Taylor Prell and Sam Egerton come in.