The Nailers won Tuesday night's replay 3-0 and face a trip to Ilkeston on Saturday, September 22.
But Duffield wants his side to carry on their good form in FA competitions by beating hosts Loughborough tomorrow.
"The win over Matlock Town was great – but will mean nothing if we go and lose at Loughborough tomorrow," he said.
"We'll be looking to build on the plus points from that game and take them into the Trophy fixture.
"We felt that we should have beaten Matlock on Saturday, as we shaded the second half.
"The replay felt more like a pre-season friendly and wasn't quite as intense. You usually back the team from the higher level in a replay but we won comfortably.
"Being successful in the cup competitions does come with its down side – we'll be playing catch-up in the league for the rest of the season.
"However, we'd much rather be in the FA Cup than out of it. And it does bring in a lot of revenue for the club."
Only defender Dan White is a doubt for the Loughborough trip. White took a knock in the warm-up before last Saturday's game and was replaced by Richard Adams, who retained his place for the replay.
Striker Jordan Ball could also be in the starting line-up after scoring twice against Matlock.
The 19-year-old former Doncaster Rovers player impressed Duffield with his match-winning performance.
"Jordan had played a lot of games in succession and was starting to look a little tired," said Duffield.
"We had him on the bench last Saturday and he did well when he came on, so I had no hesitation in starting with him in the replay.
"I guess he had a point to prove and he did it in the best way possible.
"Jordan is well thought of at the club and we're all pleased for him."
Meanwhile another Belper favourite, striker Jon Froggatt (pictured) , could be back in the side within the next few weeks as he continues to make progress following a knee injury.
Froggatt, who scored 33 goals in all competitions for the Nailers last term, has missed all of the current season but is desperate to make a return to the side, according to Duffield.
"Jon was the leading goalscorer in the league last season and is desperate to return," said Duffield.
"He's kept himself fit and is about another couple of weeks away from training with us.
"What we don't want is to rush him back too soon in case he's not quite ready.
"But Jon is already aware that, as far as scoring goals goes, he's nine games behind everyone else.
"Jon is an important player for us and having him back will be a big boost."
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