That is the verdict from Graeme Souness, who was speaking to Simon Jordan about United's woes in recent years.
The Liverpool legend said: "I've said it to Mourinho. I said: 'Do you wish you kept Ibrahimovic?'
"He looked at me and said: 'Why do you say that?'
"I said: 'Because he was your main man who kept them all… [gestures with finger in a circle].
"I can remember watching a video - I was at Sky at the time - he had a strong personality. He was doing an interview for Sky, Ibrahimovic.
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"And you know, he is extremely confident, he's got presence, big guy, and [Paul] Pogba came in and was making [gestures with hand and face].
"He dismissed him like a little boy and Pogba left the room with his tail between his legs.
"I thought, 'he's your man in the dressing room, someone who will point the finger and be big enough to put the would-be superstars in their place'."
Mourinho took charge of United in 2016 but was gone after two and a half years, getting the sack in December 2018.
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During his time at Old Trafford, he won silverware by beating Ajax in the Europa League final and lifting the League Cup in 2017 - Ibrahimovic scoring twice in the 3-2 victory over Southampton in the final.
In his first summer, Mourinho signed Ibrahimovic in a marquee transfer window which also Eric Bailly, Paul Pogba and Henrikh Mkhitaryan arrive.
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But it was the big Swede who made a big impression, instantly becoming a cult hero at United where fans loved him despite signing a one-year deal.
That was extended by another year but a serious injury towards the end of the season wrecked any chance of making a similar impact and he was released in March 2018 - Mourinho was sacked nine months later.
United have won just one trophy since - the Carabao Cup last season.
The former Paris Saint-Germain star scored 29 times for the Red Devils across two years, though he made just seven appearances in his second season.
Among his many clubs that he played for as well as PSG and United, he also starred for Barcelona, AC Milan, Inter Milan and Juventus during an extensive career.