Halifax-born Morgan Smithies, the 18-year-old Wigan Warriors loose forward, and St Helens’ Matty Lees are the other names on the list put together by the England Performance Unit.
The winner, who will be revealed at the Super League Awards evening on October 6, will be chosen by the rugby league media.
Full-back Walker - who was on a three-man shortlist last term - has become a first-team regular at Rhinos and established himself as one of Super League's most exciting attacking talents, cementing his place in the England Knights squad again.
But team-mate Newman, still just 19, has enjoyed a true breakthrough campaign at Headingley.
Having helped England Academy defeat the Austra;ian Schoolboys last winter, he has made a place his own for Leeds, giving their coaching staff enough confidence to allow England centre and captain Kallum Watkins to leave for Gold Coast Titans in June.
Huddersfield-born Newman has scored nine tries in 22 appearances and been promoted to the England Knights squad.
Half-back Trueman, meanwhile, has gone from strength to strength after last year’s success, illustrated by his brilliant hat-trick as Castleford beat Hull FC to put one foot in the play-offs on Friday.
The uncapped 20-year-old has been selected in both the England performance squad and also the Great Britain training squad.
Impressive prop Lees, 21, spent time on loan at Sheffield Eagles last year but is now very much a regular for League Leaders’ Shield winners St Helens who hope to push on to Old Trafford.
Similarly, no-nonsense forward Smithies - who hails from Halifax amateur club Siddal - has been a revelation for Wigan since debuting earlier this season, delivering all-action performances that bely his tender years.
Players have to be under 21 at the start of the season to qualify for Young Player of the Year.