I think this is a solid pick up as a back up. He is a defender and a shot blocker. When Tim Duncan hits the pine they have no real presence in the middle so that right there seems like a good enough reason to go after him.
Though in the article it said he can guard 'longer, bigger centers' in the West. He was man handled by Dwight Howard so I had to look at that comment a little funny. The problem in the West isn't the size of the big men as much as it is their speed. 7 footers like Gasol and Dirk (yes I know Dirk is not a center) are very quick for their size. Ditto for Amare Stoudamire (again doesn't play the 5 but can) Yao Ming, even though he won't be playing this year, would have been too big for him. Carlos Boozer is likely too strong for him (much like Dwight was). While he will hold his own the writer seems to be overstating what Ratliff can do at 36 years old.