That was the view of Knights boss Gary Thornton, who reckons the Hertfordshire outfit have made big strides since joining the Championship One ranks ahead of the 2013 season - as shown by the fact they currently sit fourth, below only the big three, with a draw at Oldham probably their most notable result.
Several of their players are largely unknowns, having come through the club's ranks, but other inclusions in their side tomorrow are Jy-Mel Coleman, the former Keighley and London Skolars half-back who had a spell at Huntington Stadium in 2010, James Cameron, who was at Whitehaven last year, and Chris Clough, the former Knights second-row who can be erratic and dangerous in equal measure. They will also have Dan Lizouli, a former Knights academy player from Scarborough, at loose-forward.
Last week, Coleman kicked a late drop goal to beat Gloucestershire All Golds, Cameron was named in the Kingstone Press Championship One Team of the Week ahead of York's James Haynes, and Clough made a decent debut on loan from Hunslet.
Hemel are without key Aussie recruits Mitchell Barbera and Ben Thorburn - both long-term injury absences - plus Ciaren Clement-Pascal, while former Featherstone prop Maloney, a Marine in the Armed Forces now based in Colchester, is also unavailable.
Nonetheless, Thornton has warned his men to avoid a repeat of the complacent performance that brought defeat to another expansion club, Oxford.
"They don't go away. They have lots of enthusiasm, even if they fall behind, and they never pack in," said Thornton of the Stags.
"They have an Australian coach in Troy Perkins and so they try to do the right things. He gets them organised and they try to play to good structures and to a pattern.
"James Cameron is a good player, they have a big loose-forward (Eddie M'Baraga) who looks strong and Jy-Mel Coleman has lots of tricks up his sleeve.
"They have a couple of dangerous hookers, Michael Brown (centre) has played at this level, and they also have Dom Maloney on their books who will be a big player for them if his plays."
Hemel were formed in 1981 and, having played - and won titles - in the London League, the old Alliance first division and National Conference Three, finally made the step up to semi-pro level last year. Their crowds have apparently fallen as prices have risen to Championship One levels, but they still have a bigger budget and have added to their squad accordingly.
They also have three teams in the mini age group and three in the London Junior League, as well as an under-20s academy team.
Thornton said: "They seem to be a very good club, and they've progressed since turning semi-pro. They're fourth in this league - they're no mugs."
Hemel edged All Golds 21-20 last week at the end of a scratchy game in which both sides turned the ball over too often.
Perkins said: “We know what we need to improve on and that’s taking our opportunities and hanging onto the ball a bit better. We’ve been making it difficult for ourselves."
He added: “We’ve never played York before but they’re a side that is right up there with Hunslet and Oldham as one of the teams tipped to win the league."