"We have been in talks with Yuvraj about the possibility of him playing Twenty20 cricket this summer," Angus Fraser, Middlesex's director of cricket, told 'Cricinfo'.
"The contract is not in place at this moment in time, but we're in communication, and it seems to be going quite positively," he added.
Tendulkar had refused the club's offer to prolong his international career.
The Twenty20 Cup group stages are scheduled from June 1 to July 18 and the final of the event will be played in August.
Middlesex won the 2008 Twenty20 Cup.