In 1952, Buhtz became the second German to play in Italy's Serie A – the first had been 1860 Munich's Ludwig Janda. For five years, "il tedesco" (the German), as the fans called him, would play for AC Torino, earning as much as 150,000 DM per season, an amount of money that a player in Germany "would have had to play a decade for".
Buhtz was one of the stars of the newly formed Torino team that had to rebuilt after 18 players had died in the Superga air disaster in 1949. Buhtz quickly became a regular and scored about 20 goals per season. In 1957 he left Torino for Switzerland, where he was player-manager for FC Young Fellows in Zurich and AC Bellinzona.
After his playing career, Buhtz became a full-time manager. This development was already on the horizon when he was player-manager in Switzerland. Between 1962 and 1985, Buhtz went on to manage 13 clubs in Germany and Turkey.
He began his managing career at Oberliga Südwest club Sportfreunde Saarbrücken and led them to a respectable 6th place. After the season, he signed a contract with Borussia Neunkirchen who had finished second in the 1962–63 season and were controversially omitted from the newly formed Bundesliga. Buhtz' team won the Regionalliga Süd in 1964 and they were thus promoted to the Bundesliga. After finishing mid-table in their first season, the team was relegated following a 17th place in 1966.
Following the relegation, Buhtz left the club and took over as manager of Hannover 96, another Bundesliga side. With Hannover, Buhtz reached a 9th place in 1967 but was fired on 12 February 1968. Buhtz' work at Hannover had suffered from the fact that in October 1967 the club had already signed a new manager for the 1968–69 season.
In July, Buhtz became manager of Regionalliga West side Wuppertaler SV, the club he would manage for the next six years. However, the relationship got off to a rocky start, when Buhtz was not present for the start of training on 9 July 1968, despite having set the date himself. Under Buhtz the club constantly improved, eventually winning the league and qualifying for the play-offs for the Bundesliga. Here, Wuppertal won all eight of their matches, a feat unmatched in all 11 seasons that saw a promotion to play-off. After the promotion, Buhtz extended his contract until 1 July 1975. In their first year, Wuppertal reached a sensational 4th place finish, and took part in the UEFA Cup. But in the second year the team could no longer keep up their performance, and on 20 October 1974 Buhtz was sacked following a draw at his former club Hannover 96. Wuppertal had been in 11th place at the time, but they kept slipping and finished 16th, eventually being relegated the following year.
At the end of the year Buhtz went to Turkey and took over Beşiktaş J.K. with a contract running until June 1975. With Beşiktaş he finished 5th in the league, but the club won the Turkish Cup for the first time. Originally, Buhtz had intended to return to the Bundesliga in July 1975, but instead stayed on as Beşiktaş manager. However, in January 1976, Buhtz was sacked and in February took over as manager of then 2nd Bundesliga Nord side Borussia Dortmund. This was not intended as a long-time assignment and in April that year Buhtz signed a 2-year contract as manager of 1. FC Nuremberg, starting in June. Buhtz led Dortmund to a second place in the league, allowing them to take part in the promotion play-offs against the second-placed team of 2nd Bundesliga Süd: 1. FC Nuremberg. In view of the fact that Buhtz had already signed a contract with Nuremberg for the next season, he was sacked before the play-offs.
At Nuremberg, Buhtz reached only a 5th place in 2nd Bundesliga Süd in 1976–77, but in the following season the club finished second and qualified for the play-offs on the 37th day of the season. However, like in Dortmund, Buhtz was sacked before the play-offs began. His next station was 2nd Bundesliga Süd side Bayer 05 Uerdingen where he took over in October 1978. Again he finished second in the league, and this time was not sacked before the play-offs, but instead celebrated promotion to the Bundesliga in 1979. However, Uerdingen did not play a great role in the Bundesliga. They finished 15th in 1979–80 and an 18th place in 1980–81 meant relegation. Two matchdays before the end of the season, Buhtz was sacked.
Alemannia Aachen, Stuttgarter Kickers and Fortuna Köln
In December 1981, Buhtz was the fourth manager brought in at Alemannia Aachen. Aachen were in 8th position when Buhtz took over, but he could not noticeably improve their position and finished 9th. In the following season Aachen started well, but after a slump in results, the club lost touch with the promotion ranks and Buhtz was sacked. In January 1983, 2nd Bundesliga side Stuttgarter Kickers signed Buhtz on a contract running until June of that year. Buhtz won his first match, but in the long run he could not get the club out of their 2nd Bundesliga dejection. After a catastrophic beginning of the 1983–84 season with only 1 win in 13 matches, Buhtz was dismissed on 22 October 1984. After his spell in Stuttgart, where Buhtz had worked with future stars such as Jürgen Klinsmann or Guido Buchwald, he all but retired, only taking over at 2nd Bundesliga side Fortuna Köln for a few months in the 1986–87 season.
^Ralf Piorr (15 February 2008). "Klinsi stand heulend vor mir" (in German). 11Freunde.de. Retrieved 2009-01-06. "Mit einer Ausnahmegenehmigung spielte ich bereits als 16-jähriger bei den Senioren von Fortuna Magdeburg."
^"Kurz notiert". Hamburger Abendblatt (in German) (Hamburg, Germany). 7 June 1975. p. 9. OCLC85355780. Retrieved 6 January 2009. "Entschädigung für Trainer Horst Buhtz, der ursprünglich am 1. Juli seine Tätigkeit in der Domstadt aufnehmen sollte, jetzt aber lieber ein weiteres Jahr in der Türkei bleiben will."
^"Trainerwechsel". Hamburger Abendblatt (in German) (Hamburg, Germany). 17 April 1976. p. 8. OCLC85355780. Retrieved 6 January 2009. "Horst Buhtz ... unterschrieb beim deutschen Fußball-Rekordmeister 1. FC Nürnberg einen Zweijahresvertrag."