Afridi picked 11 wickets-joint highest for Pakistan in T20 World Cup 2022.
Afridi had to hobble off the field after bowling one ball in his third over as he had previously tweaked his knee while taking a catch in the outfield.
Although an official diagnosis is expected only after Pakistan has returned home, it appears highly unlikely that Afridi will be available for the home Tests against England and New Zealand this season.
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The left-arm pacer had returned to action in the T20 World Cup 2022 after a three-and-a-half-month layoff after injuring his knee during the Sri Lanka Test series in July. His rehab was completed in time for the World Cup, and he started Pakistan's campaign at the marquee tournament slowly, feeling his way back into form.
He picked 4 for 22 against Bangladesh, 3 for 14 against South Africa, 3/24 in the semi-final against New Zealand, and 1/13 in the final against England until the injury. With 11 wickets, he was Pakistan's joint-highest wicket-taker in the competition with Shadab Khan.
His right knee is currently believed to be in a brace. The PCB said it would take some time to properly assess the injury before providing more information on the matter. It has been said that Haris Rauf might be given a shot at red-ball cricket as a replacement for Shaheen.
(ESPNCricinfo inputs)