The Yorkshire side pipped Peterborough United to finish sixth in the table and secure a semi-final clash with Charlton Athletic.
Rovers look set to have a clean bill of health for the first leg at the Keepmoat Stadium on Sunday.
Ian Lawlow, sidelined since January with a shoulder injury, and Joe Wright, ruled out with ankle issues, are both back in full training.
Doncaster are the long shots with the bookies – at odds of 5/1. Charlton and Portsmouth are both 5/2 with Sunderland 13/5.
“We’ve been underdogs all season,” said Doncaster manager McCann, 39. “Right from minute one.
“Peterborough hired a serial promotion winner in Steve Evans and sacked him. Then they hired another serial promotion winner in Darren Ferguson.
“This is what we’re up against – real experienced managers in this league. This group has been written off right from day one and we’ve just proven everyone wrong.
“We’ve proven we can challenge for promotion, that we can finish in the top six.
“You know what? Everyone will write us off in the play-offs. We’ll probably be the team people look at and say: ‘Doncaster have got no chance’. We’ll see.”
Joe Aribo and Karlan Grant scored in a 2-0 win at The Valley in November.
A John Marquis own goal was cancelled out by Malik Wilks in the reverse fixture between the two sides.
“They were far better than us at The Valley,” said McCann. “We’ve come a long way since then and we probably should have beaten them at our place.
10“It’s going to be a good game and we’ve got to make sure again we get the game plan right.”