"Whoever gets the manager's job will know that a visit to our place will be a stern test of character for the whole team," the former England Under-21 international said.
"That's because Croft Park will be such a culture shock for them compared to Premier League grounds - right from the cramped changing rooms and the proximity to the pitch of our brilliant fans, who will be in their faces.
"I'm sure the new manager will want to play a very decent team because if they send their reserves up here we'll bank on ourselves to give them a really good game.
"They will have to put out a strong side and it will give the manager an opportunity to see just what his new players are made of." Fenton, 34, is able to look forward to a welcoming of his old club to the Northumberland coastal town thanks to a dramatic 1-0 victory over Bournemouth, but is realistic about the prospects of another upset.
"We're under no illusions," Fenton said. "They're on £50-60,000 a week. Our lads get between £100 and £200 a game! It will be a day out for the lads playing against some of the best players in the Premier League.
"But Croft Park will be a leveller and they certainly won't enjoy coming here. It's a world away from a Premier League ground and especially Ewood which is known as one of the best pitches. Here the ball bobbles all over the place.
"To be honest you can't even contemplate a bunch of lads from Blue Square North beating Blackburn, but we will do our best, enjoy the day and set up to get them on the break. We won't be stupid enough to put three up front and go for them."
Tyneside-born Fenton is the Geordie whose goals for Blackburn effectively ended Newcastle's title challenge under Kevin Keegan but rates the defeat of Bournemouth that came courtesy of Ged Dalton's last-minute winner second only to his greatest achievement.
"This result is as good as everything, with the exception of Wembley when I helped Villa beat Manchester United in the 1994 League Cup final," Fenton said.
"That's simply because the bunch of lads we have and seeing the enjoyment they get playing in front of a 4,000-strong crowd and setting up a mouth-watering game against Rovers.
"They're having a few problems at the moment but Paul Ince would have turned things round. They had their reasons for sacking him and only time will tell as to whether or not they have made the right decision.
"Our manager, Harry Dunn, wouldn't do a bad job but my message to Rovers would be 'Hands off our Harry'." The tie, on Monday, Jan 5, will ensure the Cup run will yield the Conference North strugglers more than £300,000.
Tony Platten, Blyth's chairman, told Telegraph Sport: "Win, lose or draw we will be talking about £160,000 just for the televised rights. Like the FA, we're loving it because we've had a lot of financial problems in the past."
Five facts about Blyth Spartans
1. The club was formed in September 1899 and club secretary Fred Stoker suggested the name Spartans after the Greek Spartan Army to inspire their own footballing warriors.
2. Blyth Spartans are one of the most famous clubs in FA Cup history thanks to a run to that culminated in a fifth-round replay against Wrexham at St James' Park before a 42,1670-strong attendance in 1978.
3. Blyth shipyards built numerous ships for the Royal Navy during the First and Second World Wars, including the first aircraft carrier, HMS Ark Royal in 1914.
4. The port of Blyth dates back to the 12th century and still prospers, shipping paper and pulp from Scandinavia for the newspaper industry.
5. Blyth's most notable supporter is local Labour MP Ronnie Campbell.