The Rams were beaten by West Yorkshire rivals Bradford Bulls last weekend as they now prepare for the challenge of York City Knights
York are one of the sides tipped to reach the Championship play-offs but have suffered two defeats in their opening three league games.
They recorded their first win of the season with a thumping 64-16 victory at Swinton Lions.
“The quality of opposition has gone up each week. From Whitehaven to Widnes to Bradford and now to York next week.
“The games don’t get easier and that means we have to be better.”
A poor first-half display proved costly for Dewsbury against Bradford but Greenwood was able to take plenty of positives from their second-half display at the Tetley’s Stadium.
He added: “We have to take heart from the second half and some positives. There is no point kicking the lads twice.
“Look we know we weren’t good enough in the first half. We fixed some bits up at half time, and improved in the second half. It’s gone now though and we now need to look at York.”
The fixture kicks off at 7.30pm on Sunday and will be streamed live on Our League.