They were missing 11 senior players when defeating Huddersfield Giants 18-12 on Thursday night to keep alive their hopes.
It meant Leeds stayed in sixth place but they face a real battle to hold on to that final play-offs spot with just five games remaining.
Injured England scrum-half Luke Gale and Tonga centre Konrad Hurrell are likely to miss the run-in with injuries and England prop Mikolaj Oledzki and utility Liam Sutcliffe have both already seen their seasons ended.
But forward Morgan Gannon, 17, excelled against Giants in a pack that also included fellow academy products Jarrod O’Connor and Sam Walters. Stand-off McLelland, 21, also made his mark on a rare appearance.
He is out of contract at the end of the season and, though head coach Richard Agar has said he wants him to stay, there has been speculation he could return to hometown Castleford Tigers.
Either way, with Gale missing, McLelland has a chance to impress and he did that with a brilliant run to set up Ash Handley’s try against Huddersfield.
McLelland said: “It’s been a long time coming but it was a good game to come back in to.
“We’ve a lot of lads out injured, not just half-backs. We’ve a lot of young lads getting an opportunity which is pleasing to see and hopefully we can be remembered as the team that got us into the play-offs.
“I just want to enjoy my time playing. I’ve not been able to have an opportunity like this in the last three years so I’m just seeing it as my opportunity and my chance to start playing regular footy with a lot of my close friends.
“I just want to reiterate it’s so pleasing to see all the young lads – Sammy Walters, Jarrod, Morgan Gannon all getting a shot and that’s just to name a few. Obviously Harry (Newman) is back from injury as well and, for me, I’m just hopeful that next crop of players can come through, take their chance and be remembered for our play-offs push.
“If we all have that common goal and work really hard off the field and at training and turn up for each other at game day, we won’t go far wrong. We’ll leave everything out on the field.”
Leeds visit Wigan Warriors on Wednesday before going to Wakefield Trinity on Monday week.
They paid a fee for McLelland in 2018 having briefly switched codes from Castleford’s academy and played for Scotland’s Under 20s side during his time with Edinburgh.
Asked about how he looks back on those decisions, McLelland – who spent most of 2019 on loan at Featherstone Rovers and has struggled for game-time with Rhinos – said; “Hindsight is a funny thing.
“If I know what I’d known now, would I have given it more of a crack? Would I have stayed?
“I’m just happy the way it panned out and I’ve met friends at Leeds who I’ll be mates with for years to come and hopefully I’ll play with them for a long time.
“Looking back, it was the right thing to do at the time and I try and not live with any regrets.”