United lost 4-3 to St Mirren on Sunday and are without a home win in 10 SPL matches, yet victory at Aberdeen on Wednesday in the final match before the winter break could turn the momentum in favour of Peter Houston's side, who have in recent campaigns made late-season charges up the table.
"Aberdeen got a good victory against Dundee, but we've got to go there and hopefully take something out of the game," Rankin said.
"We need to start picking up points and start picking up wins. It's about momentum in this league and we need to get the momentum going quickly.
"We're sitting eighth, but the way we're looking at it we're nine points off second.
"We know if we put a run together, which we can, which we have done in the past, we're confident enough to say we can get to second place and push for a European place again.
"We just need to put a run together, get a few wins and push ourselves up the table."