The Super Eagles captain, John Obi Mikel, may not be available for Friday's high profile friendly against the Polish national team, officials have said.
The Super Eagles' Radisson Blu Hotel camp in Wroclaw has become a beehive of activities following the arrival of 22 players and the beginning of training sessions on Tuesday.
Technical and backroom staff, alongside six players opened the camp on Monday, but the facility came alive with the arrival of goalkeeper Francis Uzoho; defenders, Kenneth Omeruo, Elderson Echiejile, Stephen Eze, Abdullahi Shehu and Chidozie Awaziem; midfielders, Joel Obi, John Ogu, Ogenyi Onazi, Uche Agbo and Wilfred Ndidi, and forwards Ahmed Musa, Moses Simon, Odion Ighalo, Kelechi Iheanacho and Victor Moses on Tuesday.
Nigeria -based goalkeeper Ikechukwu Ezenwa and South Africa -based Daniel Akpeyi are expected on Wednesday.
A statement from the NFF on Tuesday indicated that Skipper Mikel is unlikely to make it to Wroclaw as he has been working hard at renewing his work permit in China, where he plays for Tianjin Teda.
Team Administrator Dayo Enebi Achor told thenff.com on Tuesday: "We all had been hoping that the renewal would come in good time for him to fly to Poland. As it is now, it is not likely that he would make the trip."
Midfield Trojan Oghenekaro Etebo is injured, and Egypt-based Junior Ajayi, who was unable to secure visa into Poland, will fly directly to London for Tuesday's clash with Serbia at The Hive, Canons Park.
The team trained twice on Tuesday, with the same schedule for Wednesday, before Thursday's training at match time inside the Municipal Stadium in Wroclaw. The match kicks off at 8:45 p.m. (Nigeria and Poland are on same time zone) on Friday.
Friday's showdown inside the 43,000 -capacity stadium formally opens the first phase of the Super Eagles' preparation for the 21st FIFA World Cup finals, taking place in the Russian Federation June 14- July 15, this year.
After Tuesday's game with Serbia in London, the three-time African champions will play a send-forth match against the Democratic Republic of Congo in Nigeria, before flying back to London for a prestige clash with England's Three Lions at Wembley on June 2.
Four days later, they will come up against the Czech Republic at their final training camp in Austria, and another friendly game is on the cards before the squad jets out to the World Cup finals on June 11.
Nigeria's team base camp at the 21st FIFA World Cup finals is located in Yessentuki, Stavropol territory in the southern region of the Russian Federation.