The Premier League is back from its World Cup break on Monday, and already this season we have seen a number of under-21 stars who have broken through to make a name for themselves.
Arsenal's Ethan Nwaneri became the Premier League's youngest player when he came on as a substitute in the 3-0 win at Brentford in September at 15 years, 5 months and 23 days, breaking the record previously held by Liverpool's Harvey Elliott (16 years, 30 days) when he was at Fulham.
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But while Nwaneri might have to wait a little longer before making the full step up to the first team, here's a list of 10 youngsters aged 21 or under who, having already been given opportunities in their respective first teams, have a chance to impress further in the new year.
Romeo Lavia, 18, defensive midfielder, Southampton
Arguably the most impactful teenage newcomer, the Belgian midfielder signed for £12 million this summer from Manchester City (who included a reported £40m clause to re-sign him in the deal.) He has shown no signs of timidity after being exposed to Premier League football as part of a struggling Southampton side and though the sample size might be small -- six starting appearances as an injury kept him out of action in September and October -- Lavia has impressed against the likes of Tottenham Hotspur, Chelsea, Manchester United and Liverpool.
Dynamic, technically gifted and safe in possession, Lavia presses, wins back the ball (six ball interceptions per 90 minutes) and distributes with measure, intelligence and precision. His well-taken goal against Chelsea -- he controlled a cleared corner neatly with his left foot before expertly curling it into the right corner from the edge of the box -- proved a telling snapshot of his maturity.
Alejandro Garnacho, 18, forward, Man United
Thrust into the spotlight against Sheriff Tiraspol in the Europa League, Garnacho's man-of-the-match performance gave him a chance to fulfill his obvious potential under Erik ten Hag. The United manager spoke afterwards about the teenager's need to improve the defensive aspect of his game "in the pressing part, in the counter-press, in the defensive transition." But he also praised his new attitude, which suggests Garnacho may get more chances.
Scoring a late goal to beat Fulham 2-1 a few weeks later cemented his position and the Argentine forward has the skills to cause problems for defenders: pace, trickery, and a desire to run at his opponent every time he gets the ball. He favours his right foot too much and still takes too many step-overs when in possession, but his idol is Cristiano Ronaldo and you can see why the 18-year-old plays the way he does. He could be the key to replacing the now-departed Ronaldo in the United XI.
Fabio Carvalho, 20, attacking midfielder, Liverpool
After helping Fulham win promotion, Carvalho arrived at Anfield for around £5m last summer ready to make an immediate impact. However, partly due to the unsettled nature of Liverpool's attacking set up and due to the step up in competitiveness, it may still take time before we see a consistent contribution from the Portugal U21 international.
There have been flashes of his talent: he showed off his opportunism with a 98th-minute winner against Newcastle, while his volley against Bournemouth highlighted his remarkable technical ability. Whether fielded as an inverted winger on the left or as a central attacking midfielder, he habitually radiates creativity and has a natural appreciation to drift (in a Philippe Coutinho-esque manner), receive and create between the lines.
Wilfried Gnonto, 19, forward / attacking midfielder, Leeds United
Leeds fended off competition from numerous European clubs to land the Italy international for a modest €4.5m from FC Zurich in the summer. But apart from setting up the winner in the 4-3 win against Bournemouth in November, we've yet to see a great deal from the teenager who played in Inter Milan's youth teams. Based on his intrinsic talent, however, there should be a lot more to come.
Gnonto has mainly been deployed on either wing, but is effective wherever he can find space. Bursting with intensity and energy, he executes his actions -- be it dribbles, flicks, lay-offs and sprints -- with high speed and favours power and urgency when it comes to finishing. Hard to unbalance, tenacious and determined, he is a fine ball-carrier who runs at defenders with maximum conviction.
Amadou Onana, 21, central midfielder, Everton
With 50+ league matches already under his belt in Germany and France -- let alone Everton paying a hefty €35m transfer fee to sign him from Lille in the summer -- Onana understandably arrived at Goodison with high expectations. Though his performances so far have been comfortably reassuring rather than spectacular, it's not hard to see that the Belgium international (who came off the bench twice in the World Cup) already plays like a fully developed senior player and possesses all the makings of a top central midfielder of the future.
Not only is Onana pleasing to watch -- he carries the ball with elegance and his natural, smooth athleticism allows him to effortlessly drift past the pressure in midfield -- he's also positive in his passing. He has won nearly 60% of his challenges so far this season and averages three dribbles per 90 minutes, so can make a mark either as a No. 6 or No. 8.
Rico Lewis, 19, right-back, Manchester City
On the evidence of seven first-team appearances, City boss Pep Guardiola clearly holds the England under-19 right-back in high regard. Among other fine performances, Lewis scored in the Champions League win against Sevilla and put in an assured, mature outing in the win over Chelsea in the Carabao Cup.
On top of his almost seamless adaptation to first-team football, Lewis appears to feature all the requirements to excel at the highest level: agile and resourceful in short spaces with a fine touch. While his coaches point to a fine mental approach, he's also a natural at combination football. And while there's work to be done on his one-on-one defending, his explosive pace often comes to the rescue.
Nathan Patterson, 21, right-back, Everton
Since making his Premier League debut at the start of the season, the Scotland international has come a long way in making Everton's right-back role his own. Primarily recognised for his pace and ability to exploit space down the right flank, Patterson has looked reasonably comfortable at the highest level, bringing freshness and spark.
While he may still lack sufficient physical strength to be more efficient in defensive duels, the former Rangers man links with the midfield and times his off-the-ball movement well to find the right positions from where he can send the ball into the box.
Armel Bella-Kotchap, 21, centre-back, Southampton
The €11m signing from Bochum started the season well and was outstanding in the 2-1 win against Leicester City in August, which led to a senior call-up for Germany (he was an unused member of the World Cup squad.)
While his fearless style of defending is obvious, his eight interceptions per game, 70% success rate from challenges and aerial dominance also rank up there with the top centre-backs. On the flip side, Bella-Kotchap needs to become more reliable with the ball and still commits too many individual mistakes, but he has already become an important player for Southampton.
Malcolm Ebiowei, 19, winger, Crystal Palace
Signed on a free transfer this summer as his contract expired with Derby County, the England under-20 winger has, perhaps surprisingly, already been gifted three Premier League cameos for his new club. With strong balance and upper body strength, Ebiowei has potentially match-winning traits in his game and it's clear to see why Palace boss Patrick Vieira has followed his development.
While he has an over-reliance on his left foot and is guilty of some poor decision-making on the ball, his instinctive dribbling skills coupled with precise crosses and set-piece accuracy from his favoured wide-right position make him a dangerous opponent and an exciting prospect.