The Newcastle defender is ramping up his comeback from long-term injury.
The Frenchman suffered a horror knee injury against Crystal Palace back in April and has only recently returned to training.
The U23s were in league action against Boro's equivalents, drawing 2-2 on the night.
It was the inclusion of Lejeune that piqued fans' interest though, with many eager to see him return to the first-team as soon as possible.
He was substituted off at the interval, but that was pre-arranged and Newcastle will be hoping to increase his minutes in matches over the coming weeks.
The centre-back is a composed and talented player at Premier League level and will be a major boost to Steve Bruce's options when he is fully fit.
Encouragingly for supporters, U23s head coach Neil Redfearn was complimentary about the player after last night's match.
He told The Chronicle: "He showed some real class at times and was very good. He is an outstanding player and some of his touches were excellent. He stepped in and out of defence and played passes through were great.
"None of the goals were down to him. He did really well to play that length of time considering he's been out for so long."
These fans are excited to hear of his return, taking to Twitter over the last 24 hours to share their thoughts...
So happy to see this man again— Shay (@Saintbazza10) October 28, 2019
Quality footballer!— Mark Austin (@TPTMerch) October 28, 2019
Brilliant to see,Toons no.1 defender back in the ball game ⚽️— CHRIS (@LANGAS1892) October 28, 2019
Look at him man— The Geordie Boot Boy (@BootGeordie) October 28, 2019
Massive player for us. Come back stronger. ⚫️⚪️⚫️⚪️— Paul White Photo (@PaulWhitePhoto) October 29, 2019
Great to have you back, a class act— Simon Horn ⚫⚪⚫⚪ (@SimonHo91784269) October 29, 2019
Welcome back! ⚫⚪— ToonArmy (@toonarmy_com) October 29, 2019
can't wait for you to be back on the pitch with the 1st team!!!— NixaMattR (@NixaMattR) October 29, 2019
Get in son best player at the club! can you play up front?— Geo (@pgnufc) October 29, 2019
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