Slovenia have confirmed they will be without the experienced duo of Matjaz Smodis and Ivica Jurkovic at next month's EuroBasket.
"It's certainly a big loss for us because they are both very important players," Slovenia's team manager, Tone Krump, said to PA Sport.
"Both players have signed contracts with Russian teams and in both cases, the people from their clubs have insisted that they didn't play the Eurobasket."
Smodis, a 2.05m forward who had been linked with a move to the NBA after helping Climamio Bologna clinch the Lega A crown in Italy, signed for CSKA Moscow.
The 25-year-old played in 1999 and 2001 but missed out on EuroBasket 2003 with a back injury.
He did not appear in any of Slovenia's six EuroBasket qualifying games.
The absence of Jurkovic robs Slovenia coach Ales Pipan of an even more important player as the 32-year-old power forward/centre was a key player in their qualification games.
Jurkovic, who has just joined Lokomotiv-Rostov this summer, played in all six European qualifying games for Slovenia.
He has appeared for his country in the last three EuroBaskets.
Slovenia were put on notice in Podgorica over the weekend that they are not yet good enough, losing to Lithuania, Serbia & Montenegro and Croatia in the ProMonte Super Cup.
After the defeat to Croatia, Pipan said: "We made lot of mistakes, took too many bad shots. Our biggest problem is defence, though."
Pipan will be hoping to see improvement in the Efes Cup in Istanbul.
The Slovenians take on Italy on Tuesday before facing Serbia & Montenegro two days later.
Pipan, who currently has 13 players in his roster, is expected to name his final 12-man squad by September 11.