The two sides meet at Highbury for the first time tomorrow, with the Cod Army just ahead of the U’s in the npower League Two table.
Fleetwood have had a meteoric rise up the football pyramid.
Just eight seasons ago they were playing in North West Counties Division One, the same level as Letcombe, Headington Amateurs and Easington this season.
They broke the 100-point barrier in winning the Blue Square Premier last season, but are in no mood to stop progressing.
They recruited heavily last summer and have been one of the busiest clubs in the country during the January transfer window.
The club’s transfer record was broken to bring in striker Jamille Matt for a fee reportedly in the region of £300,000.
Yesterday they were linked to Hull City midfielder Paul McKenna, who would be their fifth signing of the month.
It means that despite averaging less than 3,000 for home games, Lewis believes Fleetwood should be viewed as one of the division’s heavy hitters.
He said: “They’re a really good side and have come up the leagues.
“They’ve got about 30 players in their squad to choose from and it doesn’t matter that they’ve come up very quickly and have only just come into the Football League.
“Fair play to them, they’ve invested well and bought a player for about £300,000.
“Make no mistake about it, they’re a big club in this league, they’re a really ambitious club who are trying to get promoted.”
United’s playing budget is more modest, but they would go above Fleetwood with a win.
Last weekend the U’s were due to host Rotherham, another side who have overhauled their squad this season.
Competing with the big spenders is a challenge for the club, but Lewis insists they do not pay too much attention to what their rivals are doing.
He said: “To be honest you don’t think about it too much, until you come up to play against them.
“Then you look at how they’ll line up and what squad they’ve got, that’s when sometimes with those clubs who invest you go ‘look at who they’ve got’.
“But then you realise we’re a good club with some good players and we’re in form.
“So even though it’s going to be a tough game, we’re going to be confident going there.”