Shahzad, 32, retired hurt during Afghanistan's warm-up game against Pakistan
on May 24, but subsequently played the team's first two World Cup matches.
He underwent a knee scan during the warm-up match against Pakistan. In the two matches that he did play, he was out for a three-ball duck against Australia
, and made 7 off 12 against Sri Lanka
. Afghanistan lost both matches.
But while Shahzad has reportedly insisted that he was fit, the ACB chief executive, Asadullah Khan, was adamant that there had been no foulplay in dropping the wicketkeeper-batsman.
I was removed from the 2015 World Cup [he wasn't selected for fitness reasons] and now this one as well. I am going to consult with friends and family. My heart isn't in cricket anymore
"It's absolutely wrong to say that he was unfairly dropped," Asadullah told ESPNcricinfo. "We have given a medical report to the ICC to prove that he is unfit, and after thorough deliberation they allowed us to replace him. He is our main batsman, who can make a big difference with the bat, and it was a really difficult decision to drop one of our key players."
Shahzad's medical report, a copy of which has been accessed by ESPNcricinfo, does confirm that he has a mild ACL strain on his left knee.
Asadullah explained that since attaining full membership, Afghanistan had increased their focus on fitness. "Now that we are full members, our priority will be on fitness, in international and domestic cricket," he said. "We can't carry unfit players. We understand Shahzad was not fully fit when he still went on to play two games and this is not acceptable anymore."
Shahzad, after returning to Afghanistan, launched a broadside against his ouster while speaking with local media, accusing the ACB higher management for the move. "I went to a doctor in London and he drained my knee of some fluids, gave me a pill and said that I could play after resting for two-three days," Shahzad told media in Kabul.
"I had a practice session, bowled, batted, and had a keeping session... had lunch with my team-mates, and then sat down in the team bus (to return to the hotel) only to see the ICC press release on my phone saying I am out of the World Cup," he explained. "That was the moment when I found out that I was unfit.
"I asked the manager, who asked me to put the phone in my pocket and talk to the doctor. The doctor looked at me helplessly and said he couldn't do anything. I don't know what is the problem. If they have a problem, they should let me know. If they don't want me to play, I will quit cricket.
"I don't see myself playing anymore. It's a dream to play the World Cup. I was removed from the 2015 World Cup [he wasn't selected for fitness reasons] and now this one as well. I am going to consult with friends and family. My heart isn't in cricket anymore."
Shahzad is no stranger to controversy, despite having been a pivotal figure in Afghanistan's extraordinary journey through the ranks to Test status. He missed out on playing during a large chunk of 2017 following an ICC suspension over a doping violation
. Last year, he was found to be in breach
of the ACB's code of conduct when he played in a local Peshawar tournament, and was asked to reside permanently in Afghanistan or risk having his contract terminated.
Umar Farooq is ESPNcricinfo's Pakistan correspondent