"The boys from Churchill Brothers and East Bengal couldn't arrive together with the group, courtesy the AFC Cup schedule. They need to recover fast and stay fresh," Koevermans said.
The national team members from Churchill Brothers and East Bengal are representing their respective clubs in the Asian Football Federation's second tier continental competition.
Koevermans believed that acclimatisation is important for such tournaments as they involve frequent travelling.
Koevermans said the team's entire focus is on the opening encounter, on March 2, against Chinese Taipei.
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"The sessions were of very high intensity and everyone adjusted well. At the moment we are focusing on Chinese Taipei. It's the first game of the tournament and a really important one for us," the Dutchman said.
Asked whether injuries to Arnab Mondal and Sandesh Jhingan during the preparatory camp would affect team's plan, Koevermans said: "Unfortunately injuries are always a part of any training camp. They were freak ones but we need to move on. That's why we called for a bigger group of players.
"Even after Sandesh (Jhingan) was ruled out, we called for an extra defender (Rowilson Rodrigues) to ensure we had enough quality players for the tournament.