Belgian goalkeeper Koen Casteels, 22, was once a star while compatriot Thibaut Courtois was the struggler.
The roles have since reversed.
Courtois just won the Premier League title with Chelsea, whereas Casteels has been registered by three clubs in 2015, illustrating the uncertainty of his career.
When Courtois Was Behind Casteels
Nine years ago, Courtois probably was an insubordination—one bad performance or a negative judgement away from being released by Genk, as goalkeeping coach Gilbert Roex recalls.
"When [Courtois] was 13 or 14 years old, there were some doubts he would ever make it," Roex said, per Matt Law of The Telegraph. "Some coaches raised their doubts, and at a certain point the [Genk] youth directors were even thinking about letting him go."
Having Casteels, a burgeoning star, in their system would have given Genk the leeway to cut Courtois, whose development had stalled.
It was not just Genk's coaching staff, as Courtois' mother, Gitte, also worried for her son.
"I was even thinking Thibaut was just not [mentally tough] enough for football," Gitte said, per Kristof Terreur of The Observer (h/t The Guardian). "But his dad and my father have always encouraged him to work hard and never let his head drop."
Courtois proved he belonged in the Genk academy, but Casteels was still regarded as the "more promising" goalkeeping prospect, per Bjorn de Cock and Steve Wuestenbergs of Benefoot.
By the time Casteels and Courtois turned pro, the once-astronomic gap was now nip and tuck for then-Genk manager Franky Vercauteren.
"It was quite strange coming into [Genk], where you had two young goalkeepers of that quality in the squad," Vercauteren said, per Ciaran Kelly of The 42. "I chose Thibaut [over Casteels], and it's always a special memory because it proved to be the right choice."
Vercauteren's decision to back Courtois was a profitable outcome for then-Genk director Dirk Degraen.
"We received an enormous offer [from Chelsea] that gave us no choice but to let [Courtois] leave," Degraen said, per Rob Parrish at Sky Sports. "I have mixed feelings about this transfer. Genk wanted Thibaut to stay a bit longer."
The seven-digit gap in transfer fees Genk received for Courtois and Casteels represented the chasm in quality that rapidly expanded between the two goalkeepers.
"Chelsea see me as the successor to Petr Cech," Courtois said, per London 24. "It won't happen in one or two years, but in three, four or five years."
Courtois was right.
Casteels is to Courtois what Leroy Smith was to Michael Jordan—the catalyst to an all-time great career.
What captivated then-Hoffenheim director of football Ernst Tanner was Casteels' physical tangibles and his reputation as a goalkeeper with elite upside.
Tanner must have looked at Casteels, a 6'6", 190-pound member of the Belgian golden generation, and thought: "Cash cow!"
"We are pleased to have signed such a talented young keeper in Koen Casteels," Tanner said, per Hoffenheim's website. "He belongs to the top group of talent in Europe in his position."
Casteels' 2011/12 season | Hoffenheim's third-choice goalkeeper behind No. 1 Tom Starke and backup Daniel Haas.
Courtois' 2011/12 season | Usurped both Joel Robles and Sergio Asenjo to become Atletico Madrid's undisputed No. 1 while on loan from Chelsea. Won the 2012 UEFA Europa League.
Despite Casteels' imposing size, he is a mild-mannered and unassertive person, according to Hoffenheim goalkeeping coach Zsolt Petry.
"Koen has been coached very well, but he still lacks a little bit of aggression and perhaps the belief in himself," Petry said, per Hoffenheim's website. "Koen is a really good guy, a nice kid and very well-educated. There's no doubt he has huge potential, and we hope he can fulfil that here."
Arriving from Werder Bremen, Tim Wiese walked into the Hoffenheim No. 1 position, which Casteels meekly accepted.
"I'm excited about training with Tim," Casteels said, per Hoffenheim's website. "I will try to learn as much as possible from him."
Described as "Porsche-driving, toned [and] solarium-tanned" by David Gohla at Kicker (h/t Jonathan Wilson's book The Outsider: A History of the Goalkeeper), Wiese's out-of-control ego was diametrically opposed to the naive Casteels.
Wiese provided Casteels a manual on how to self-sabotage your career.
Having prodded the footballing public with his look-at-me antics as if he was a heel in World Wrestling Entertainment, Wiese could not deal with the backlash to his life falling apart.
"Tim, join us for an away trip—we take care of the booze," read a banner from the Hoffenheim fans alluding to Wiese's alleged alcohol addiction, per Bild (h/t Stephan Uersfeld at ESPN FC).
"...Every time we [Hoffenheim] lost, it seemed it was my fault; I was being analysed and criticised, not the team," Wiese said, per Bild (h/t Eurosport). "It was like being in a horror movie. The pressure was inhuman."
The failure of Wiese, who later quit football to be a professional wrestler, granted Casteels a four-game and a five-game run in the Bundesliga.
Hoffenheim management were not convinced by Casteels, who played as if he was on tenterhooks.
Cue the loan signing of Heurelho Gomes, who at the time was a Tottenham Hotspur outcast.
"The discussions with Hoffenheim's representatives went well," Gomes said, per the Bundesliga's website. "They seemed to have faith in my ability."
It was an indictment on Casteels, who was given back the No. 1 position by default (again) after Gomes broke his hand.
Casteels' 2012/13 season | Unimpressive in three separate starting spells spanning 16 games. Did not qualify for Kicker's Bundesliga goalkeeping rankings. His rating, in theory, would have placed him at No. 19 out of 19 shot-stoppers.
Courtois' 2012/13 season | Successive season as Atletico Madrid's No. 1. Named La Liga Goalkeeper of the Year. Won the 2013 Copa del Rey.
In November 2013, Hoffenheim extended Casteels' contract until 2017 to protect his transfer stock.
He was still the worst Bundesliga goalkeeper, according to Kicker.
Casteels suffered a major blow when he collided with Adrian Ramos in Hoffenheim's 1-1 draw against Hertha Berlin.
"The only thing I remember is feeling the pain in my leg immediately after making contact [with Ramos]," Casteels said, per Hoffenheim's website. "I knew straight away that something was broken."
Tragically, it was Casteels' last Bundesliga moment in a Hoffenheim shirt.
Casteels' 2013/14 season | Not even in the stratosphere of Bernd Leno's extraordinary reflexes, Manuel Neuer's ball-playing ability, Marc-Andre ter Stegen's prodigiousness or Ralf Fahrmann's physical presence. Casteels' breaking his leg was feared to be career-debilitating. Missed 2014 FIFA World Cup.
Courtois' 2013/14 season | Started 37 La Liga games for Atletico Madrid and played 56 games in all competitions. Won La Liga title. Started five games at the 2014 FIFA World Cup.
Like a punter cashing out before the bet pans out, Hoffenheim director of football Alexander Rosen had no intentions of seeing if Casteels would bounce back.
Hoffenheim had effectively ended Casteels' tenure by signing Oliver Baumann, a goalkeeper who can be world-class one match and amateur hour the next.
He was still an upgrade over Casteels.
Shopping Casteels around, Rosen found a buyer.
"It's not been an easy situation for Koen," Rosen said, per Hoffenheim's website. "The transfer [to Wolfsburg] is a new [beginning] for him."
Wolfsburg manager Dieter Hecking is comfortable with Diego Benaglio as the No. 1 and Max Grun as his deputy.
This was why Wolfsburg loaned Casteels to Werder Bremen, presumably to challenge Raphael Wolf.
Bereft of credence in his own ability, error-prone and having no command over his defenders, Wolf is out of his depth.
Kicker have placed Wolf at the bottom of their goalkeeper rankings.
Yes, even Casteels, who has been a punching bag for Kicker, has a better rating than Wolf.
"The last few days were long..." Casteels said when explaining the novelty of being involved in a three-team transfer, per Werder Bremen's website. "I will give my all for the good of the team."
Like Courtois saying he would replace Cech, Casteels has lived up to his promise.
Taking advantage of Alejandro Galvez's nonexistent marking, Rafa latched onto the cross and powerfully directed toward goal.
In perfect position, Casteels dove to his right, tipped the ball over with his left hand and denied a clear scoring chance for Paderborn.
It was a 2-2 draw, so Casteels produced a match-saving moment.
In the past, Casteels might have palmed the ball into his own net.
2014/15: 4.3 saves per game.
2013/14: 2.8 saves per game.
2012/13: 2.5 saves per game.
Averaging a career high in saves per game, Casteels is Werder Bremen's temporary answer to Courtois.
When not specified, statistics via WhoScored.com.