The Latics boss made nine changes to his side that drew at Fulham on Saturday, and was delighted with his side's performance as they eased past League One's Bournemouth with a 1-0 win on Tuesday night.
"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," Martinez 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."
Martinez praised midfielder Roger Espinoza and Manchester United loanee Angelo Henriquez, who slotted into his side with ease.
"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 shocked Championship leaders Cardiff City.
"It's going to be a difficult tie," Martinez said
"They deserve all the media attention they get. To beat the Championship leaders is not an easy task."