Another parallel - Leverkusen: (stats from statto.com and transfermarkt)
2001/02 - League runners-up with 69 points, behind champions Dortmund (70); Champions League runners-up (lost to Real Madrid); from having a shot at the treble, they eventually lost on all 3 fronts (DFB-Pokal final - lost to Schalke) in a remarkable choke job. "Neverkusen" as they say.
2002/03 - Finished just above relegation with 40 points (Dortmund are now on 16 with 15 games to go...)
2001/02 - scored 77 goals (ranked #1) and conceded 38 (joint #4)
2002/03 - scored 47 goals (joint #6) and conceded 56 (joint #4 from bottom)
I wasn't following them much but was vaguely aware of the contrast in the seasons; digging up the records now, you can see some of the same traits again.
In 2002/03:
- lost their 01/02 top scorer Ballack (17 goals, 8 assists) to Bayern Munich
- lost their 01/02 top creator Ze Roberto (4 goals, 17 assists) to Bayern Munich
- Neuville went from 13 goals in 01/02 (#2 scorer) to 4 goals in 02/03 (and that was still #2 !)
- Ulf Kirsten went from 11 goals (#2 scorer) to just 3 league games and 1 goal in 02/03; I'm not sure if he was injured but he retired at the end of the 02/03 season anyway (36 years old)
- Their back four (Zivkovic, Juan, Placente, Lucio) played 30, 24, 23 and 21 games, while Nowotny played only once (injured I think for the season); so not a really settled back four at that time. Lucio would leave 2 seasons later to join... yep, Bayern Munich.
This is how their season went:
Leverkusen bounced back to finish 3rd the following season.
Dortmund so far: