This is an excellent signing. Darnell Dockett can rush the quarterback, and it’s not easy to find defensive tackles who can do that effectively. Better to sign Dockett than to spend a first-round pick on someone like defensive lineman Arik Armstead who had just 10.5 sacks in three seasons at Oregon.
Dockett will improve the Niners’ Nickel pass rush right away. He may or may not improve the base run defense. Dockett has received poor run-defense grades from Pro Football Focus for years, although he might improve now that he’s playing next to great run defenders like Glenn Dorsey and Patrick Willis and NaVorro Bowman.
If Dockett turns out to be a liability against the run, the Niners don’t have to play him on 1st-and-10 in the base defense. Glenn Dorsey can play Ray McDonald’s old position and Ian Williams can play nose tackle. In the Nickel defense on passing downs like 3rd-and-10, Dorsey and Williams can go to the bench and Dockett can play defensive tackle next to Justin Smith.