When the Spaniard returned to the south Wales club as manager in March 2007, a few months after being released as a player, Monk was sidelined by a serious knee injury.
With the defender's contract expiring in the summer and his career at the club in the balance, Martinez had a difficult decision to make.
However, the then Swansea boss decided Monk was the man around whom he would build a new, different team. And under Martinez, Monk captained the Swans to promotion to the second tier of English football for the first time in 24 years.
Monk, in temporary charge at Swansea following the departure of Michael Laudrup, comes up against his old manager in an FA Cup fifth-round clash at Goodison Park.
"Garry was my first big decision as a manager in terms of shaping a squad," said Martinez.
"I had to decide on giving him a new contract and keeping him at the club after a very difficult injury rupturing his cruciate.
"I built a new squad around him and I knew he was the perfect captain and it was important he kept that role in the future.
"Garry has always been a responsible character in that dressing room.
"When I took over at Swansea there was a real need to bring in different talent and I decided to bring players from abroad, and when you do that you need to make sure you rely on a British core.
"Garry was at the centre of it and he has been very influential in the dressing room since then.
"He was the one that I knew could do that role perfectly well even though he was coming of the back of a very difficult injury. I knew he had all the elements that were needed to build that team full of different cultures and mentalities to work together as a winning side."
Monk is unbeaten in his two matches, importantly winning his first game against south Wales rivals Cardiff before seeing Swansea draw at Stoke, and Martinez respects what he has done in his short time in charge.
"He had that leadership, that DNA of being able to control a group, and being a captain in a club like Swansea where it is so involved with the community is an intense surrounding," he added.
"It prepares you for that and Garry always responded very well.
"He has had a really strong start (as manager). The Welsh derby can be as intense as it gets for a new manager but it was a really good start.
"To be unbeaten against Stoke is another difficult game in the league. He is showing this group is reacting well and is in a very good moment of the season.
"He has had time in the last few months, because he hasn't been involved playing football, and that has probably helped him to look from a distance and get his thoughts together and develop a good method of work.
"It didn't surprise me Garry started his career so well.
"We had a conversation when he was appointed but he doesn't need any advice.
"He is very thorough and he puts a lot of time into everything he does and he knows exactly what he does.
"He has respect from everyone at the club and the dressing room and as a manager that is vital to enjoy your role."