Sunderland's Premier League trip to Manchester City on Wednesday was postponed due to inclement weather, allowing Poyet's star men an extra break ahead of the last-16 cup clash.
But despite the unexpected the rest for his players, Poyet said he would stick with his original plan and make several changes for the visit of Southampton.
"I was looking forward to giving a few players opportunities and that will not change," he told The Sunderland Echo.
"We have a few players who need to play and deserve to play but, for different reasons, they haven't been able to.
"I'm talking about players like (Emanuele) Giaccherini and (Ignacio) Scocco. They both need minutes, so we're going to use that game for this.
"But it will all be first-team players, we will not be taking the game lightly. I hope that we win it so we don't have to have a replay."
Sunderland, who will be without the suspended Wes Brown, have had a relatively straightforward run to the fifth round, with home victories over Carlisle United and Kidderminster Harriers to date.
And they have enjoyed even greater success in the League Cup, with Poyet's men due to take on Manchester City in the final at Wembley on March 2.
Sunderland remain in trouble in the league, however, sitting 18th, albeit with a game in hand over most of their rivals.
Southampton, on the other hand, are enjoying a fine season, and are eighth in the Premier League table.
Mauricio Pochettino's men come into the game on the back of an eight-match unbeaten run in all competitions, including wins over Championship outfits Burnley and Yeovil Town in the third and fourth rounds of the FA Cup.
The two sides met last month in the league, with Sunderland coming from two goals down to claim a 2-2 draw.
And Southampton assistant manager Jesus Perez says his side have learned their lesson as they look to reach the last eight of the competition for the first time in nine years.
"We know Sunderland very well," he said.
"This will be the fourth time we've met them (this season) but, when you are playing a lot of competitions, that's always a possibility.
"We are ready to face them. We have learned from every game against them. We review and analyse every game to determine how we have to improve in case we have to repeat situations."
