The 22-year-old Spanish international has faced multiple injury setbacks in recent seasons since making a significant impact as a teenager in 2019.
"Ansu Fati has sustained a muscle injury to his right hamstring during training on Wednesday. He is anticipated to be unavailable for around four weeks," stated the La Liga leaders, Barcelona.
Fati will miss the upcoming Champions League match against French team Brest on November 26, along with La Liga fixtures against Celta Vigo, Las Palmas, Mallorca, and Real Betis.
Additionally, winger Lamine Yamal, who recently surpassed Fati's record as the youngest player and goalscorer for Barcelona, is also out for about three weeks due to an ankle injury.
Veteran striker Robert Lewandowski is dealing with a minor back issue, while Marc-Andre Ter Stegen, Andreas Christensen, Ronald Araujo, and several others are also currently injured.