"I'm not going to tell you anything," Harbaugh said when asked about Whalen's status at his weekly news conference. "As soon as we tell you, you tell Notre Dame. There's no advantage to doing that."
Harbaugh has taken a tightlipped approach to injuries this season, revealing as little information as possible in interviews.
That's the same approach he is taking with Whalen, who appeared to hurt his left arm while being tackled following a short catch in last Saturday's 68-24 victory over Wake Forest.
Whalen was not listed on the three-deep depth chart for the 16th-ranked Cardinal (3-0). But Harbaugh wouldn't say anything about his status for Saturday's game at Notre Dame, saying it would give the Fighting Irish a competitive advantage.
"I would want to know that about the status of every player on their team, whether they're going to play, what percent they are, how many plays they're going to play, how they're going to be used," Harbaugh said. "That's valuable information."
Whalen had 10 catches for 113 yards and one touchdown before being sidelined. Whalen led the team with 57 catches for 926 yards last year and has 109 career receptions for 1,558 yards and six touchdowns.
He provides even more intangible help to an offense that is averaging 51.7 points and 475.3 yards per game this season.
"Whales is the leader on offense for us. He's our captain," quarterback Andrew Luck said. "He's been there and done it all at Stanford. It will be a serious blow if he's out for a while. We have guys who can step in and fill that role. He knows he's going to have to be out there coaching the guys up. Whatever happens I think we'll be fine."
Cushioning any blow that Whalen's absence would present was last week's healthy return of big-play receiver Chris Owusu, who missed the first two games with a reported knee injury.
Owusu caught touchdown passes on his first two drives of the season last week against Wake Forest. He turned his first reception into an 8-yard score and also made a leaping 35-yard touchdown catch later in the first quarter.
Owusu added a diving 22-yard catch over the middle as his speed brings an added dimension to an already high-powered offense.
"It was great to get him into the mix early, get him a touchdown, get him in the end zone," Harbaugh said. "It was really good to have him back. He's just one of our best players. You try to put him in as many situations as you can for him to have success."
Owusu had five touchdown catches last year and also returned three kicks for scores. He did not return kicks in his first game back but Harbaugh said that could come soon as Stanford looks to get him even more involved heading into the toughest stretch of the season.
"He has a lot of speed and explosiveness that adds a lot to the offense," Luck said. "I don' think the wide receiver corps was lacking with him out, but he definitely brings the level of play up."
After visiting Notre Dame on Saturday, the Cardinal travel to No. 5 Oregon next week and host No. 20 Southern California the following week.