The former San Francisco 49ers quarterback will make his debut for the AFC West side when they face the New Orleans Saints this evening.
The 29-year-old told the team's website: "It will be nice to hit other people. It will be good to get back into game mode, even if it's pre-season.
"Preparing for the game and travel, there's a lot that goes into that to get ready to play."
Defensive end Allen Bailey added: "It's exciting to get to hit another opponent. We've been going the last couple weeks against the same teammates, so it'll be good to see a different coloured jersey and hit somebody else."
The Chiefs finished the 2012 NFL season with the worst record in the league, winning just two of the 16 regular season games.