Martinez made nine changes to the Latics side which drew their last Premier League game at Fulham and they eased past League One side Bournemouth 1-0, courtesy of a fantastic strike from Mauro Boselli.
The Cherries put up a valiant effort across both legs, but Martinez was delighted with the performance from the fringe players he brought into his starting line-up.
"The young players and those who needed the minutes showed that they're ready to step up their competition in the squad which is very pleasing to see," he said.
"If you're going to be successful on more than one front then you need quality players competing for their place and that's what we have.
"An outstanding finish from Mauro Boselli was the difference and in the second half, as we expected, Bournemouth came at us a lot more, but we looked a threat on the counter and were unfortunate not to get a second goal."
Two of those players coming into the side were making their full debuts for Wigan and Martinez thought both midfielder Roger Espinoza and Manchester United loanee Angelo Henriquez slotted into his side well.
"They looked comfortable and as though they already have a good understanding with each other and the rest of the team," he said.
"Roger never put a foot wrong, controlled the midfield area with ease and combined his style in possession with an aggression off the ball to win it back, covering the ground well with a real tactical awareness.
"Angelo's acceleration made him a threat throughout the game. His penetrating runs were outstanding and it was unfortunate he couldn't find the back of the net but worked hard for the team.
"The pitch didn't help either team but to see new players come in and perform in such a manner was a real plus."
Wigan will make the short trip to Macclesfield in the fourth round after the Blue Square Premier side stunned Championship pacesetters Cardiff.
Martinez was an unused substitute when Wigan recorded a 2-0 win over Macclesfield in the 1998/99 season, with the Latics also winning their away fixture when the two sides were both in the third tier, and the Spaniard has praised the non-league side for their cup run.
"It's going to be a difficult tie," Martinez told BBC Manchester.
"They deserve all the media attention they get. To beat the Championship leaders is not an easy task."