Northland forwards Josh Goodhue and Tom Robinson, and five-eighths Harry Plummer from Auckland and Stephen Perofeta from Taranaki have extended their contracts.
Goodhue and Perofeta have signed for next season, while Robinson and Plummer have signed until 2023.
Each of the players could achieve 50 caps for the side by the end of their contracts.
Segner, from Germany, has been in New Zealand since 2017 when he took up a school exchange position at Nelson College. He captained the school, the Crusaders Under-20s and has been a New Zealand Schools' and Under-20 representative.
Plummer has managed to play in every Super Rugby game during his three years at the Blues. That includes 14 starts and 30 times off the bench.
Perofeta joined the side in 2017 and marked his debut by scoring the winning try after coming off the bench for the Blues to beat the Reds in the first Super Rugby game played in Samoa. Injuries have been a frustration for him and have restricted him to 30 appearances.
Goodhue debuted in 2017 and has made 38 appearances for the side, while Robinson has played 34 times since his debut in 2019.
Coach Leon MacDonald said: "These four players are all incredibly important for our team on and off the field. They are still young but now experienced Super Rugby players with a significant number of games under their belts.
"They are now senior players who will continue to have a growing influence on this team as players and as leaders. They are a vital cog in the Blues' machine and I am delighted they have all decided to extend their stay."
MacDonald said he saw Segner during his final year as Makos coach and believes he has all the attributes to be a success.
"I was impressed with him as a schoolboy and have followed him since. Not only does he have all the physical attributes and skill set, but he also has an outstanding work ethic.
"Anton is a young leader on and off the field and will be an excellent addition to the group of young talent at the Blues. These young guys have played together at higher honours and will be the future," he said.
Segner, from Frankfurt, said he was still pinching himself at his chance.
"You don't get too many Germans coming here to take up rugby. It has all seemed pretty surreal to me," he said.
"There's a massive opportunity not just to play but to learn from other players as well. The Blues have three All Black loose forwards, and I will be looking to learn from them and develop off them.
"To be honest, ever since going to school, I have been in and around the Crusaders' environment. When the Blues opportunity came up, I was attracted to do something different, to challenge myself in another environment, and embrace that challenge," he said.