The midfielder departs as a free agent after he and the club could not agree terms on a fresh deal.
The 25-year-old was initially on trial at Chesterfield after injuries had prevented him from playing much football in the last few years.
He was loaned out to Tamworth to improve his match sharpness and that proved to be a shrewd move as he hit the ground running when he returned to the Spireites at the start of October, impressing on his debut in a 1-1 draw at Wrexham.
He was unknown to many at the time but he provided a real bundle of energy in the middle of the park, snapping into tackles and not giving the opposition a second on the ball. His beetroot-coloured face at full-time told you he left absolutely everything out on the pitch. He played with his heart on his sleeve, as if every game was his last.
Kellermann, who is half-German, played like an angry man, and he told me it must be his ‘German blood’.
He can play, too. He was excellent in the first-half of the season as Town topped the table, playing in an advanced number 10 role at times, roaming, pressing and hustling.
His most memorable moment came in the FA Cup second round as the Blues upset League Two Salford City, firing the second goal into the roof of the net from the tightest of angles to send the boys to Stamford Bridge. ‘Oh Jimmy, Jimmy’ rang out loud and proud from the away end.
After the game he told me in an interview that he was about a week away from quitting football altogether before Chesterfield came calling. What a shame that would have been.
We all know what happened in the second-half of the season, but ‘Kellers’ kept plugging away, scoring a superb swerving half-volley from the edge of the box against Yeovil Town.
Manager Paul Cook started him in 16 of his 20 matches in charge – two of which he was suspended for – so I was expecting him to stay, but it sounds like a new deal would have been on reduced terms. If the plan had been used to him as a squad player, I don’t think that would have suited him and he needs to continue to play games after a rotten time with injuries.
As for his angry side, I got a little glimpse of it after the brilliant play-off win against Halifax when he sarcastically suggested my ratings would still be ‘twos and threes.’ I’m sorry, Jimbo!
Whatever his next move is, his new club will be getting a fully committed, hard-working midfielder who you would want alongside you in the trenches.
The last time I saw him he was walking over to the away end at Solihull, after going back into the dressing room, to hand over a shirt to a fan. I think that says a lot about him as a person.
The Spireites have sadly had some half-arsed players on their books in the last five years, but Kellermann is definitely not one of them. All the best to him.