"Our pre-season program worked well and the lads are looking really fit, I was really pleased with the fitness levels showed against West Brom last week.
"The lads have probably been ready to kick things off for a few weeks now and it is nice to get those last few pre-season games out of the way so we can fully concentrate on League Two."
Some members of Rovers squad will be making their Football League debut this weekend but Darrell insists that won't be an issue for his players.
"We are faced with challenges like this all the time but we won't be letting our lads use that as an excuse. We want to stay strong as a group and show that we have that mental strength that we showed last season.
"At the end of the day, it's 11 men vs 11 men and the team that works hardest usually walks away with the three points.
After a solid end to the 2014/15 season and a summer of strengthening, Chris Wilder's Cobblers are tipped by many to be near the top of the table in May and Darrell is calling on the same fighting spirit that helped his side out of the Vanarama Conference last season.
"They [Northampton] finished last season well but you just don't know with these things. There will be certain teams that will be fancied to be up there but we will see how things are after the 46 games.
"My aim is to be part of that group of teams at the top of the division fighting away for promotion and it is vitally important that over the first 10 league games we pick up as many points as possible and that starts with Northampton this Saturday.
"If we don't have the best start like last season you have to show what your made of and come through that. Throughout the season there will be different challenges for everyone but it is about staying strong as a group."
To watch Darrell's full interview on the new Gas PlayerHD, click on the video below: