The former Tottenham midfielder is back in England but this time without any of the hype that surrounded him six years ago
As he struggled to deal the pace and physicality of the football, Holtby was left frustrated by a lack of game time and, in hindsight, admits he reacted poorly.
"It was definitely frustrating because I had good spells where I felt I deserved more game time. But I did expect more of myself, I had more expectations to succeed," Holtby told The Independent earlier this year.
"I thought I had the quality but maybe I was a bit naive. I made too many rash decisions. I wasn't as professional as I am now in a lot of things.
"There's a lot of things that I’ve gained now over the years and I think if I was there now, I would act differently."
So desperate to play, Holtby jumped at the chance to join Fulham on loan in early 2014 – despite the fact the club found themselves at the wrong end of the Premier League table.
However, Felix Magath felt Holtby wasn't up for a relegation battle and he accused the young German of not being "a fighter".
It was a surprising accusation as scrapping is something Holtby has been doing his whole career.
From being told he was too small for football as a teenager and being sent packing from Borussia Monchengladbach's academy, to a succession of relegation battles with Hamburg, Holtby has regularly punched above his weight.
What's more, Holtby's first taste of top-flight football came at Schalke in 2009 under Magath.
Subsequent loan spells to Bochum and Mainz would follow, with Holtby truly finding his feet at the latter under the guidance of Thomas Tuchel.
Forming a deadly trio with fellow young guns Adam Szalai and Andre Schurrle, Holtby helped Mainz claim seven straight wins in the Bundesliga in 2010.
Their most famous victory during that spell came against Bayern Munich, with the three attackers celebrating like a rock band following one of their goals and earning the tag of the 'Bruchweg Boys'.
After a strong season with Mainz, Holtby returned to Schalke and despite being deployed in a deeper midfield role, still managed to stand out, scoring six league goals in the 2011-12 season.
The following campaign would see the young German then turn heads in the Champions League, with a particularly strong performance coming against Arsenal in November 2012 as he claimed both assists in a 2-2 draw.
From there, Holtby hit a hurdle he would struggle to recover from, as he unsuccessfully chased the Premier League dream in England and was forced to return to Germany with his tail between his legs.
Only signed in September, he has featured just twice off the bench for the club and while clearly facing another fight for minutes in England, Holtby is hopeful his best is not yet behind him.
"It’s never too late to come back to high standards like the beginning of my career," Holtby told The Independent.
"I used to play in the Champions League, for the national team. Then, you’re a hotshot. You always want to come back to that. I think I’ve still got that in my locker."