1987–99: Early career

Schaaf began his managerial career while still an active player, taking care of Werder's youth sides. After this he proceeded to manage the reserve team which competed in the third-tier Regionalliga Nord,^[6] before succeeding Felix Magath on 10 May 1999 as the senior side's coach,^[7] with the club under serious threat of relegation until the last day of the season: he managed to steer the team clear out of relegation, going on to win the campaign's domestic cup immediately afterwards, defeating Bayern Munich in a penalty shoot-out.^[8]

2000–04: Building up the team and the Double

Schaaf led Werder to the double in 2003–04,^[9] as well as the team's first-ever DFB-Ligapokal two years later.

2004–09: European adventures

From 2004 the club managed to qualify five consecutive times for the UEFA Champions League,^[10] coming short in 2008–09 but winning the cup (his third as a manager – fifth overall – and Werder's sixth), thus qualifying for the following season's UEFA Europa League.^[11] That same season he also guided the club to the 2009 UEFA Cup Final, lost 1–2 to Shakhtar Donetsk after extra time.^[12]

2009–13: Final seasons

On 14 December 2009, Schaaf signed a new contract with Werder Bremen.^[13] He led the side to the third place in the league and the playoff stages in the 2010–11 Champions League, as well as to a second straight German Cup final, which was lost to Bayern Munich.^[14]

Schaaf left Werder on 15 May 2013 by mutual consent after finishing a disappointing fourteenth in the domestic championship, ending 14 years in charge of the club and ending his 41-year association with the club since joining as an 11-year-old youth player.^[15] He oversaw 645 games as a coach during his stint, finishing with a record of 308 wins, 138 draws, and 199 losses^[16] and leading it to six major trophies and six appearances in the Champions League,^[17] and was linked to the organization for four decades since his days as a youth player.^[18] During the press conference where he announced his resignation, he spoke of his admiration of the club and the joy of his time spent at the Weserstadion, saying, "I had an extraordinary time here, connected with a lot of positive experiences and great successes. I would like to thank everyone who accompanied me along the way and supported me. I wish Werder Bremen a successful future."^[19]

2014–15 season: Eintracht Frankfurt

On 21 May 2014, after one year out of football, Schaaf was appointed head coach of Eintracht Frankfurt, signing a two-year contract.^[20] During the course of his first season he led his team to a ninth-place finish, being in charge of his 500th Bundesliga match in the process.^[21] Schaaf resigned on 26 May 2015.^[21] His final match was a 2–1 win against Bayer Leverkusen.^[22] He finished with a record of 12 wins, 10 draws and 14 losses from 36 games and was ultimately succeeded by Armin Veh.^[23]

2015–16 season: Hannover 96

Schaaf was appointed as the head coach of Hannover 96 on 28 December 2015, signing an 18-month contract^[24] and being formally introduced to the media after his first training session on 4 January 2016.^[24] He took over a team that was in 17th place, after they took 14 points from a possible 51 when he was hired.^[24] His first match was a 2–1 home loss against SV Darmstadt 98.^[25] Hannover then failed to score a goal in their next four matches.^[26]

Schaaf was sacked on 3 April 2016,^[27] after a 3–0 defeat to Hamburger SV.^[28] He finished with a record of one win and ten losses.^[29] His first^[30] and only win^[29] was a 2–1 win over VfB Stuttgart on 27 February 2016,^[30] and Daniel Stendel took over for the rest of the season.^[27]

2020–21 season: Brief return to Bremen

In May 2021, he returned to Bremen for one game, after Florian Kohfeldt was dismissed before the last matchday.^[31][32] On the last matchday, Bremen lost at home 4–2 against Borussia Mönchengladbach to finish 17th in the league table; hence, they were relegated to the 2. Bundesliga for the first time since the 1979–80 season.^[33]