Scott is the same age as Ratliff (will be 29 this season) and goes 6-2, 305. That makes him about 2 inches shorter, but about 10 lbs heavier than Rat. Not the ideal sized NT, but a good size for a Phillips 3-4 NT. Scott got 7 starts last season after Jamal Williams went down, and was projected to start this season before the draft. SD drafted Cam Thomas in the 5th round and I guess he made Scott expendable. They also have some guy named Ogemdi Nwagbou who took about the same number of snaps as Scott last year (althout Scott performed much better.)
In his career, Scott has 3 sacks and 83 tackles in 40 starts. Not great numbers, but should be able to unseat Siavii. According to ProFootballFocus, Scott ranked 45th out of 87 NTs playing 25% of his teams snaps. His performance ranked below Siavii's but on twice as many snaps.
Anyway, just a thought. I've never been sold on Siavii. And considering the guy will be 32 this year, a younger option might be worth a look.