The Italian hadn't played since Indian Wells in March because of a hand injury which forced him to miss the entire clay-court swing and, in Murray, faced an opponent whose own injury issues hampered him in the deciding set.
``It was the last thing that I imagined when I came here,'' Berrettini said of winning the title on his return to the tour.
Three-time Grand Slam champion Murray collided with one of the players' seats at courtside in the first point of the decider and called for the physio soon after for treatment on his left leg and hip. He took another timeout when he appeared to indicate a problem with his abdominal muscles at 4-2 down.
``This is not the way that we wanted to finish the match,'' Berrettini said, and he praised Murray's history of bouncing back from injuries. ``He showed us so many times how to come back.''
Berrettini moves to 6-3 in career finals with his second career Stuttgart title, while Murray is 46-24 in his 70th career final as he chased a first title since 2019. It was the first time Murray played a singles final on grass since winning Wimbledon in 2016.
Tournament organizers said Sunday that an investigation had begun after Nick Kyrgios said he faced racist abuse from the crowd in his semifinal loss to Murray the day before.
``No discriminating actions by the spectators are accepted,'' organizers said in e-mailed comments. ``We have expressed our regret towards Nick Kyrgios and his team and assured that any kind of discrimination is unacceptable. The incident is currently under investigation.''
Kyrgios was given a game penalty Saturday when he appeared to confront someone in the crowd during the match.
``One thing I won't ever tolerate is spectators heckling and blasting abuse to athletes. It's been happening personally to me for a while, from racist comments to complete disrespect,'' the Australian wrote on Instagram on Saturday.
(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)