Against the Golden Bears, Casto converted 5 of 6 field goals en route to 14 points. He averages 11.2 points and a team-high 6.4 rebounds per game.
"He probably played as good of basketball the last few weeks as I've seen him play," Bone said. "His focus has been extremely good. I really like the way he's playing."
If Casto is unavailable, Bone said sophomore forward Brock Motum likely would start in his place. Motum scored a career-high 19 points against Cal.
"Fortunately Brock Motum had a good game the other night," said Bone, adding that sophomore Steven Bjornstad and junior Charlie Enquist would see increased playing time without Casto. "He should feel pretty good about the way he's playing."
But without Casto, the Cougars' ability to contain Wildcats forward Derrick Williams would be even more difficult. Williams, a sophomore who is projected to be an NBA lottery pick, averages 19.2 points and eight rebounds per game.
"That's a tough one to approach," said Bone, referring to guarding Williams. "It's definitely a concern."
IF IT HOPES to earn an NCAA Tournament bid, Bone said the next three games are crucial for WSU (17-8 overall, 7-6 conference). Arizona (21-4, 10-2), is undefeated at home, but even Arizona State (9-15, 1-11) concerns Bone. The Sun Devils, who host the Cougars at 11 a.m. Saturday (TV: FSN-NW), have lost 10 consecutive conference games.
"You have an Arizona State team that has struggled, but scares the heck out of me," Bone said. "We have three tough games in a row. We need to produce."
After playing against the Arizona schools, WSU heads to Seattle to play Washington next week. Both Arizona and the Huskies are undefeated at home.
The Cougars won their previous meeting, 87-80, on Jan. 30 against UW in Pullman. But they followed that with a loss at Oregon and then were upset at home, 75-62, last week against Stanford.
Bone was asked about those inconsistencies.
"Sometimes it is disappointing, but when I look at the big picture I'm really proud of the way we're playing," he said.
That is because he said sophomore point guard Reggie Moore (wrist) and junior guard Faisal Aden (knee) have not played a full health. Both have missed practices and Bone said he believes those injuries have affected the play of both players. He said Casto also was hindered by a previous ankle injury suffered in December. Bone said the missed practice time makes it difficult for his team to develop continuity on the court.
"It's hard to grow as a team and progress when you don't have your parts every day," he said.
But other teams also are dealing with injury problems. Cal guard Allen Crabbe scored 30 points to lead the Bears to an 88-81 overtime win on Jan. 13 against WSU, but missed Saturday's rematch between the teams because of a concussion.
"We're not the only team in the country that is dealing with unhealthy bodies," Bone said.