Villa have doubled the £9 million they paid to sign the winger from Watford in January 2007, while Young is reported to have doubled his wages with a £130,000-per-week pay packet.
"It happens all the time, it's football, people come and go and you've just got to deal with it and just keep going," Delph, who described the England star as a "big brother" to him, told the Birmingham Mail.
"I don't think he could be replaced, to be honest with you. His all-round work ethic was absolutely unbelievable.
"He must have run twice as much as most people on the pitch.
"With his goals and assists it will be very hard to replace him, but if we can get somebody here half as good as him then he would still be a great player.
"You get a lot of players, who are not selfish, but do more of their work in the attacking half of the pitch whereas Youngy is up and down, when he's on the right-hand side especially, working hard for the boys.
"The lads appreciate that from a winger who has flair but still wants to graft."