The Timbers enter MLS in 2011 but need to put together a competitive playing roster before any on-field plans are made.
Wilkinson said that the club will use a few different methods in building a strong squad.
"We will be carrying 28 to 30 players. There are many ways and different mechanisms - we will be looking at potential trades and foreign signings," Wilkinson said.
"We're looking at every single one of these positions and then acquiring someone equal or better, to put pressure on these guys, to see if we can get more out of the guys we have now."