But 65-times capped Catt, who recently signed a one-year contract extension with Irish, is arguably the Premiership's form midfield operator and was a key factor behind the Exiles reaching this season's Premiership play-offs.
"Everyone says, 'He is a fantastic player, but...'. What they actually mean is, 'He's a fantastic player, but he's 34'," said Smith.
"It (his age) doesn't matter. Mike Catt has performed in 25 games for us this season - he stood up for us in the first game of the season and he's been a leader all the way through."
Smith also believes Catt's cause could be helped if Bath head coach Brian Ashton joins a new-look England backroom team prior to heading at Australia in three weeks' time. Former Bath ace Catt played much of his rugby at the Recreation Ground under Ashton.
"There is one bloke on this planet who knows Brian Ashton's attacking philosophy better than anyone, and that person is Mike Catt," added Smith.
"It wouldn't surprise me if Andy Robinson went that way. Forget Mike Catt's age, we would support his selection - nobody is respected more than Mike Catt in our dressing room."