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Joe Riley wore the smile of a cat that got the cream. Quite right, too, because in making his first appearance for Manchester United, the 19-year-old who worked his way up through the club's ranks from the age of six lived an experience that boys the world over would give their eye teeth for.

"Standing at the side, waiting to come on, just wearing your shirt with your name on the back. It's always something that any lad going through the system is proud to do," Riley said after his debut 45 minutes as a second-half substitute in a 3-0 victory at Shrewsbury Town in the FA Cup in February.

"A very good feeling."

Many United fans, of course, would rather have the here-and-now instant gratification of league and cup silverware. They're hungry for a return of pulsating entertainment at Old Trafford, not the thin, unappetizing gruel served up too often by United of late.

Still, in the absence of trophies and of coherent, consistent attacking football, the single most redeeming feature so far of Louis van Gaal's two-year tenure as manager has been his heavy use of young players like Riley: born in and around Manchester, hot-housed by the club since they were kids and thrown by the Dutchman into the deep end of first-team football.

This has been both by accident and design. Van Gaal's history of trusting young players outshines contemporaries such as Jose Mourinho. At Barcelona, the coach gave Xavi Hernandez the first of his record 767 appearances for the club. At Bayern Munich, he made a first-team regular of teenage debutant Thomas Mueller. In striker Marcus Rashford, Van Gaal appears to have unearthed another pearl this season at United.

Cruel accumulations of injuries and, some might argue, a failure to recruit or retain more senior players also forced Van Gaal's hand. Missing injured first-team players for his first official match in 2014, Van Gaal handed debuts in defense to Tyler Blackett and Jesse Lingard, both from the Manchester area, and promptly lost 2-1 to Swansea.

Riley, born in Blackpool on the northwest coast above Manchester, came on against Shrewsbury because Cameron Borthwick-Jackson, another Manchester-born product of United's academy fast-tracked by Van Gaal into the first team, was injured in the first half.

But why Van Gaal has done what he's done is less interesting than the simple fact he has done it at all. In turning to youngsters in tough times, he is perpetuating one of the club's finest traditions.

In the 1950s, Matt Busby brought though his "Babes" who helped make him a legendary manager. He gave Duncan Edwards his debut at 17. The 18-year-old Bobby Charlton scored twice on his 1956 debut under Busby — a feat that Rashford, also 18, emulated in his first match this February, a Europa League victory against Denmark's Midtjylland. And Alex Ferguson had his "Fledglings" — David Beckham, Ryan Giggs, Paul Scholes and others who made fools of those who argued that United wouldn't win with kids.

So the half-dozen youngsters debuted by Van Gaal this season and those from last season have much to live up to before they will be worthy of their own "Louis' lads" tag. Van Gaal — or whoever replaces him should United force him out this summer — should continue what he has started, keep giving young players opportunities to deepen the mark they have made, rather than simply shop on the open market for established stars and relegate the next generation to the bench.

That will allow Nicky Butt, a former Fergie Fledgling appointed in February as head of United's academy, to keep telling parents in all honesty that the club's pathway for youth remains well and truly open and that their kids might also get to run on the Old Trafford turf one day.

"Our history shows that if you continually let these kids play together, they'll just get better and better," said Tony Park, co-author of "Sons of United," a history of the club's youth system, and a United season-ticket holder for 25 years.

When one or two young players break through to United's first team, "the third one thinks he's next," Park added. "All of a sudden, everyone thinks they can do it. You get this groundswell of confidence at the next level down."

Of course, first-team places must be earned. Long-term, not all the youngsters Van Gaal has tested will be worth retaining. Some have already moved on. But Rashford, certainly, oozes class. By making Wayne Rooney drop back into midfield to accommodate the teenager up front, Van Gaal has sent the encouraging message that age and experience are secondary to talent. Lingard, Borthwick-Jackson and the strapping, athletic Timothy Fosu-Mensah, recruited at age 16 from Ajax, also look promising.

Seeing youngsters in red might not feel as worthwhile as shiny trophies but is still its own reward.

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John Leicester is an international sports columnist for The Associated Press. Write to him at jleicester@ap.org or follow him at http://twitter.com/johnleicester