Djokovic is through to only his second semi-final of a troubled campaign as he hunts his first title in 2018.
The Swiss is sparing no effort to make sure he lifts a tenth title at the event on Sunday.
Djokovic's caution comes as he sits a lowly 22nd in the ATP rankings.
World number one Roger Federer kept his quest for a 10th Halle grasscourt title alive by saving two match points to defeat France's Benoit Paire 6-3, 3-6, 7-6 (9/7) and make the quarter-finals on Thursday.
The world number one needs to lift a record 10th title at Halle on Sunday in order to remain at the summit of the rankings and assure himself the top seeding at Wimbledon starting a week from Monday.
On Friday, lawyers for Germany's three-time Wimbledon champion lodged a claim in the High Court in Britain saying that he had been appointed a sports attache for the CAR to the European Union (EU) in April.
Andy Murray gave an encouraging display in his first competitive match in 11 months after finally recovering from the hip problem that required surgery in January
With Wimbledon starting on July 2, Novak Djokovic is desperate to improve his lacklustre 14-8 record in 2018.
In order to stay ahead of rival Rafael Nadal, Roger Federer must now win the Halle trophy
Kei Nishikori worked for just under 90 minutes to beat his 159th-ranked German opponent 6-3, 7-6 (7/3).
Stanislas Wawrinka, the three-time Grand Slam champion had an obliging opponent in South Africa-born Norrie, who was given a wild card entry after rising to 79th in the rankings.
The former world number will return to action after hip surgery in January.
Federer made a return to the top ATP ranking for a sixth time through his semi-final victory on Saturday over Australian Nick Kyrgios.
Roger Federer will play for the 98th title of his career on Sunday against Milos Raonic.
Andy Murray has not played a competitive match since his Wimbledon quarter-finals exit last July.
Roger Federer needs to win one more match in Stuttgart to return to the No.1 spot for the second time this season.
Roger Federer was made to battle after a losing first set as the Swiss star made his long-awaited return to tennis
Rafael Nadal has admitted he finds it hard to make the transition from clay to grass
