"There are young players coming through at United but this is an important part of their career," Giggs told MUTV.
"When you look at the lads who came through in my age group, then those who followed; Wes Brown and John O'Shea for instance, when they got their chance, they took it.
"Once you hit 17, 18 and 19, that is what you have to do.
"It doesn't matter whether it is if you get a chance to train with the first team, or in a match as a substitute, you need to make an impact.
"You need to force the manager not leave you out of the next game."