Jim Harbaugh has described Alex Smith as "efficient" and "in control" during the Kansas City Chiefs' pre-season game against the San Francisco 49ers.
Smith was playing against the 49ers for the first time since leaving the NFC West champions earlier this year.
The 49ers head coach told the team's website: "He looked in control. He looked very efficient, very much in charge, the same Alex that we came to know and love.
"It felt a lot like going against my brother. This was different. It was personal in the best kind of way. We'll be following him."
Smith spent eight seasons with the 49ers, but lost his starting place to Colin Kaepernick mid-way through the 2012 season.