Offset language allows teams to recapture guaranteed money if the player is released and signs with another team.
"We've always had offset language in our player contracts. It's nothing new," Underwood said. "I think it is important where a high first-round draft pick is concerned, because it's the precedent. Everything that we do is precedential for the next round of contracts.
"So keeping the offset in place is something we want to be able to do going forward. And the minute you back away from the contract principle then you no longer are able to assert it going forward."
Underwood added the Titans would be giving up a longstanding principle going forward if they allowed Mariota to have offset language. Mariota remains the only 2015 first-round pick yet to sign a contract.