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...
17.
RICKY-JADE JONES. Age: 18. App 35. Goals 5. FACTS: Striker Ricky scored his first Football League goal in the final match of last season at Doncaster. He has also scored FA Cup goals at Premier League Burnley and at home to Stevenage plus twice more in EFL Trophy matches.
18.
IDRIS KANU. Age: 21. App 63. Goals 3. FACT: Idris has made 43 of his 63 appearances for Posh as a substitute.
19.
ETHAN HAMILTON. Age: 22. App 42. Goals 1. FACTS: Midfielder Ethan and Mo Eisa made the most substitute appearances (21) for Posh in League One matches last season, one more than Niall Mason. Ethan has been sent off once in each of the last three seasons.
20.
JOE TOMLINSON. Age: 21. App 0. Goals 0. FACT: Joe had an unsuccessful trial at Posh six years ago following his release from Southampton’s famed Academy programme.