Jeff Tuel started the first two games of the season, but had an injured knee and did not play against UNLV last week. Connor Halliday started in his place and led the Cougars (2-1) to a 35-27 victory.
"You'll have to stay tuned and watch very closely," Leach said. "The anticipation is killing everyone, including me.
"We're going to have a good week of practice and see how that ends up," he added.
He did say he was pleased with Halliday's progress.
"He's way ahead of schedule for guy who played only a handful of games," Leach said.
Leach is reluctant to talk about injuries and starting lineups before games. He declined to publicly name Tuel as the starter for the season opener at BYU until nearly game time.
Tuel, ranked in the top 10 in WSU's career records in yards passing and touchdowns, suffered a knee injury late in a win over Eastern Washington. He's recovered now.