Centre-back and skipper Mark Beevers is the oldest at 31 with teenage defender Ronnie Edwards the youngest of three 18 year-olds. Aaron Powell and Ricky-Jade Jones are also 18.
Here are some facts about the men most likely to be entrusted with keeping Posh in the Championship...
9.
JONSON CLARKE-HARRIS. Age: 27. App 49. Goals 33. FACTS: Jonson played over 50 times for Rotherham in the Championship, scoring his first goal at that level in a 2-1 win over Leeds United in 2014. Jonson scored from one of every 3.1 shots at goal for Posh last season.
10.
SIRIKI DEMBELE. Age: 24. App 123. Goals 26. FACTS: Forward Siriki was the first League One player to record 10 goals and 10 assists last season. He hit the first hat-trick of his career in a 5-1 win over Shrewsbury. He’d never scored more than one goal in a game for Posh before then.
11.
JORGE GRANT. Age: 26. App 0, Goals. FACTS: Midfielder Jorge (pronounced George) scored his first professional goal in his second Nottingham Forest appearance in a 3-1 League Cup defeat at Spurs in 2014. He took an incredible 16 penalties for Lincoln City last season, scoring 12 of them.
12.
JOSH KNIGHT. Age: 23. App 43. Goals 3. FACTS: Josh was at Leicester City for 15 years before moving to Posh this summer. The defender/midfielder had two loan spells at London Road, but his League debut for the club lasted just 22 minutes before he picked up an injury at Oxford.