Once a promising prospect at a club known for developing diamonds of footballers, Giovanni Reyna's time with Borussia Dortmund is up -- for right now, anyway. The 21-year-old United States international joined Nottingham Forest on loan for the remainder of the season, the Premier League club announced on Wednesday.

There's no option to make the move permanent, and in fact, Dortmund have extended Reyna's contract through the end of the 2025-26 season in the process, so there's every chance he could return to the Westfalenstadion. But there's no doubting that his past six months in Germany have been underwhelming, and a change in scenery might be just the tonic Reyna needs to jump-start his career.

How did this move came to pass in the final days of the January window? And what does it mean for Reyna, Forest and Dortmund?

Additional reporting by Julien Laurens

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How, and why, Reyna ended up at Nottingham Forest

Heading into the January transfer window amid the uncertainty of which clubs would lead the race for Reyna, there was one constant thread: Reyna wanted and needed to leave Dortmund for first-team football. Agent Jorge Mendes and father Claudio Reyna -- the ex-USMNT captain and Premier League midfielder -- took the lead in these discussions and looked at multiple options for Gio including, according to sources: Marseille, AS Monaco and Lyon in France; Real Sociedad, Sevilla and Villarreal in Spain; as well as Portugal's Benfica and then Wolverhampton Wanderers and Nottingham Forest in the Premier League. Of those, Forest, Marseille and Sevilla were the most eager.

Heading into the final days of the window, there was also interest from Italy's Fiorentina, but it ended up either Marseille or Forest as the places Reyna would go.

Marseille were in a strong position: Reyna could learn from the demanding Gennaro Gattuso and the French league suited his game, but Reyna had his heart set on a move to the Premier League. His father Claudio watched Forest's matches to see how Gio would fit in, while Mendes' good relationship with the club also helped. (He is also the agent for Forest manager Nuno Espirito Santo.)

The lack of a language barrier also contributed to the decision, and late on Jan. 31, Forest announced the loan agreement move through to the end of the 2023-24 season.

At the same time as they confirmed the move, Dortmund announced they had extended Reyna's contract through to 2026. They emphasised there wasn't an option to make the move permanent, but also that it was Reyna's wish to move on loan and try to get some more minutes, with Forest his chosen destination.

"We are happy that we have been able to extend the contract with Gio for a further year," said Borussia Dortmund sporting director Sebastian Kehl. "He is a player who has enormous skill and in whom we still see a lot of potential."

It won't be an easy ride for Reyna at his new club. Nottingham Forest have a lot to juggle: they are 16th in the Premier League and Nuno has been there eight matches after being parachuted in to help stave off relegation. Then there are the potential sanctions hovering above their heads, with the Premier League charging the club -- alongside Everton -- for breaching the Profit and Sustainability rules (PSR).

It's hardly a soft landing, but Reyna is committed and feels this is where he can get some much-needed game time.

How and where will Reyna fit into Forest's team? His versatility across the forward line will be a huge asset to Forest, but as Dortmund boss Edin Terzic said last month, Reyna wants to be regarded long term as a No. 10 or No. 8 option, which could be a problem if Nuno sticks with the current 4-2-3-1 formation. Forest's typical front three (Chris Wood, Anthony Elanga, Nicolás Domínguez) are largely interchangeable, but getting the starting No. 10 spot at Forest will be tricky. It's a position held down by the club's record signing and outstanding player Morgan Gibbs-White, who captained the team against Arsenal last time out in the Premier League.

Gibbs-White has featured in every league match this term except their 3-2 defeat to Brentford on Jan. 20, which he missed through an abdominal injury. If they stick with this 4-2-3-1, then Reyna will likely start on the flanks.

A switch in formation could work in Reyna's favour. Forest have had a host of players on international duty at the Africa Cup of Nations -- Ibrahim Sangaré (Ivory Coast), Willy Boly (Ivory Coast), Ola Aina (Nigeria), Sèrge Aurier (Ivory Coast), Cheikhou Kouyaté (Senegal) and Moussa Niakhaté (Senegal) -- while the impressive Elanga has been out injured. Once they return, it could see Nuno switch to formations he favoured during his Wolves tenure, where he preferred the 3-4-3, which switched to a 4-5-1, or the 3-4-2-1. Both could see Reyna deployed as one of a pair of No. 10s alongside Gibbs-White, the two working in tandem running off and with striker Taiwo Awoniyi.

If Nuno opts for a midfield three, then Reyna could be their new No. 8. His versatility is king here, but the hope is he'll get his time in his preferred No. 10 spot.

If Reyna's loan spell goes well, it could turn into a permanent move, but this is where things could get tricky. With no option in the deal, Reyna's prospects of a long-term stay at Forest are already somewhat out of his hands. Failing to survive the drop would mean a summer of overhaul in order to reduce their wage bill. Even if they stay in the Premier League, and given their dalliances with PSR this season, signing Reyna to a full-time deal will not be cheap. Equally, Dortmund are under no pressure to move on from the player given they have that extra year's buffer with his contract.

If Reyna impresses, it's a win-win for all involved. Dortmund would have a player back in form, and with Marco Reus's contract expiring in Germany in the summer, the U.S. international could yet be their next long-term No. 10. If he's kept on the periphery, Reyna would be on the market, and aged just 21, he'd be viewed as a safe investment, with clubs knowing they could recruit a player whose value could skyrocket in coming years.

Reyna's debut could come as soon as Sunday at AFC Bournemouth. He'll wear the No. 20 shirt, and judging by the message he sent to the Forest fans upon signing, he already feels at home in the Premier League.

"I'm ready to work hard, I'm really for the challenge and I can't wait to attack the Premier League with this amazing club. I'm Gio Reyna, and I'm a Red." -- Tom Hamilton

The Dortmund view: They're not giving up on U.S. star

Late last year, Reyna, father Claudio, his new agency Gestifute and Dortmund's sporting director Kehl met to discuss the 21-year-old American's once-bright future at Borussia Dortmund. Not long before that meeting, Reyna had departed American agency Wasserman to join the Jorge Mendes-led Gestifute, believing that new representation was needed to bolster his options on the market.

After a disappointing spell in early 2023-24, Reyna wanted Dortmund's opinion of him and his immediate future. Terzic wasn't happy with Reyna's defensive work rate; the manager expected his attacking midfielders to track back and aggressively block passing lanes in order to improve Dortmund's questionable defensive stability. What also hurt Reyna's standing in the team was that in their mind, he was showing limited improvement. All the while, Jamie Bynoe-Gittens, an emerging 19-year-old English talent, took the spotlight with his one-on-one skills and entertaining style of play on the wing.

Kehl assured Reyna that Dortmund wouldn't prevent him from going elsewhere for more game time, while at the same time working to bring Jadon Sancho back from Manchester United for a six-month loan spell. Sources have confirmed that Reyna was then offered to Premier League clubs, but interest in England was initially lacking.

As Dortmund toyed with the idea of parting ways with Reyna -- either through a permanent transfer or a loan with an obligation to make the deal permanent -- they made a pivotal decision. Rather than severing ties, ending a chapter that commenced in 2019 when the teenage prodigy made the transatlantic leap from the New York City FC academy to the Bundesliga powerhouse at the age of 16, BVB opted for an alternate course of action: extending Reyna's contract until 2026 and orchestrating a loan arrangement with Nottingham Forest.

This January transfer is not a farewell from Dortmund. The club seemingly refuse to relinquish the hope that Reyna could blossom into the next American soccer star and develop substantial value in the years to come. It's a vision reminiscent of Christian Pulisic, whose talents garnered a 64 million transfer to Chelsea in January 2019.

Even though Terzic was to an extent dissatisfied with Reyna's performances last term and early on this season, he praised Reyna's showing in Dortmund's 3-1 win over VfL Bochum last Saturday.

"You could see that Gio is capable of influencing the game from the bench," Terzic said after bringing him on for Youssoufa Moukoko after 66 minutes. "He was very confident on the ball, managed to create a few dangerous situations, but was a bit unlucky with his finishing in one or two situations."

After Reyna had established himself in Dortmund's Bundesliga team, he carried himself like someone who was capable of leading the team at some point in the future. One of his best friends in that team was Jude Bellingham, who did exactly that at a young age. Injuries and lacklustre performances have derailed Reyna's career to a degree, though, and trying to prove himself in a new environment while still staying connected to Dortmund might be the best move possible. -- Constantin Eckner