The Dutchman has enjoyed a remarkable season with runaway Eredivisie leaders PSV, who equalled a top-flight record by winning their first 17 league games.
PSV are now gunning for their first Champions League quarter-final since the 2007-2008 season, as Eindhoven fans dare to dream of emulating Guus Hiddink's class of 1988 which lifted the cup.
But Bosz will have a personal point to prove against Dortmund, who tempted him away from Ajax in June 2017, paying a Bundesliga record five million euros (£4.27m) in compensation.
The Bosz reign started brightly enough. Six wins from the first seven games led some to speculate that Dortmund could finally dethrone perennial champions Bayern Munich.
But the rot started to set in by mid-October, when Dortmund embarked on a run of five games without a win, piling the pressure on the new coach.
The domestic woes were compounded by failure in Europe, with Dortmund crashing out of the Champions League group stage without a single win.
However, the low point came on November 25, in a famous game at home against bitter local derby rivals Schalke 04.
Dortmund were 4-0 up within 25 minutes but somehow contrived to draw the game 4-4, leaving the home fans - and backroom bosses - furious.
At a board meeting the following day, CEO Hans-Joachim Watzke told booing club members: "I feel just as shitty as you all... I have never experienced anything like that."
Media slammed Bosz's 4-3-3 system and he failed to get the best out of star striker Pierre-Emerick Aubameyang, who eventually transferred to Arsenal after several disciplinary issues at Dortmund.
The die was cast and Bosz was finally sacked on December 10, after just 167 days in charge. "Bye, Bye, Bosz," headlined mass-circulation daily Bild.
'Poison in the group'
When the last 16 draw was made against his old employers, Bosz was diplomatic, describing Dortmund as a "big club" with one of the strongest fanbases in Europe.
"I still know a lot of people at the club and I'm looking forward to it," he said.
But in an interview with the Algemeen Dagblad late last year, he revealed the behind-the-scenes difficulties, notably with Aubameyang and French striker Ousmane Dembele.
Bosz said the trouble started when Dembele disappeared from training, only to surface in Monaco, where he was in secret contract talks with Barcelona.
The day after Dembele left, Aubameyang turned up late for training. And the next day. Finally, Bosz suspended him after he filmed a commercial on the pitch without permission.
"I learned from that. The situation became poison in the group," said Bosz.
After a year on the sidelines, Bosz eventually returned to the Bundesliga with Bayer Leverkusen.
In his third season in charge there, the team was top at the winter break but things fell apart rapidly after that and he was sacked again, heading to Lyon.
The pattern repeated itself and he was fired from the French club in October 2022 after a poor run of form, finally joining PSV in June last year.
PSV come into Tuesday's game at the Philips Stadium suffering a small blip in form from their flying start.
Hampered by a long injury list, they were held 1-1 by a resurgent Ajax earlier in the month. However, they remain unbeaten with a sizeable gap over the chasing pack.
They warmed up for the big European clash with a 2-0 home win against Heracles.
Meanwhile, Dortmund sit fourth in the Bundesliga but have a strong record in Europe, topping the so-called Champions League group of death ahead of Paris St-Germain, AC Milan, and Newcastle.
