Martinez paid the price for failing to get the best out of a talented young squad, and England international Jagielka said anyone hired to replace him would struggle to keep hold of the team's best players.
“There is going to be a lot of change in the playing squad,” the 33-year-old centre back told British media.
“I am not sure the squad is going to be big enough for the start of next season with the people who are leaving.”
Veteran goalkeeper Tim Howard has retired after a 10-year stint at Everton, while striker Romelu Lukaku and centre back John Stones are likely to be targeted by bigger clubs.
In addition, the likes of Leon Osman, Tony Hibbert, Steven Pienaar and Darron Gibson are all out of contract in the summer.
“I am not sure exactly what will go on but there could be double figures leaving, which is a lot,” Jagielka added.
“We are not talking about young lads either. We are talking about established first-team players. It is going to be a big change of personnel and that will play a big part in who will get the chance to manage the club.”
Everton finished the season on 47 points and 11th in the table, and were knocked out in the semi-finals of both the Capital One (League) Cup and FA Cup. – Reuters
Original source: Jagielka warns of Everton player exodus