Steve Evans said several players had pushed their claims for a starting place at Colchester in two specially-arranged friendly games on Tuesday.
He also said he was likely to make changes, despite the superb 3-1 home derby win over Notts County last weekend.
The Mansfield Town manager sent half his squad to non-League neighbours Rainworth MW on Tuesday, fulfilling a summer promise, and the rest for a behind-closed-doors game at Sheffield Wednesday.
Rainworth were disappointed when a pre-season friendly against a full Stags side turned into U21 opposition, but Evans promised he would send a full squad up as soon as possible.
“We were disappointed we couldn’t do it back in the summer. We couldn’t put the type of team up that I thought would do them justice,” said Evans.
“They are good people up there and we wanted to send players up there that would be recognised as first team players.
“It was a good exercise and we intend to be back in the summer of next year.”
He added: “We also had a behind-closed-doors game against Sheffield Wednesday at Hillsborough on Tuesday and a number were involved in that.
“It gave us the chance to have a look at one or two things – patterns of play, shapes of play, changes of formation etc.
“We told the boys after Saturday that the plan was to split the group over Tuesday. Everyone has come through unscathed, which is the first thing.
“We have people fighting for places and we’re going to have a look at it tomorrow and pick a team for Saturday.
“It doesn’t mean for one second that because we beat Notts County that’s going to be the XI that starts against Colchester. It’s a totally different game at a different venue and it’s a different formation and system of play we’re playing against.”