Adam Caplan of ESPN first reported the news on Feb. 13.
Zac Jackson of Pro Football Talk noted there was previous talk of Saleh sharing duties with Atlanta Falcons assistant Jerome Henderson, but Caplan clarified there wouldn't be a co-defensive coordinator situation.
Saleh was the Jacksonville Jaguars linebackers coach for the past three seasons. He also boasts previous experience in the NFC West since he was a defensive quality control aide from 2011 to 2013 for the Seattle Seahawks, per Marc Sessler of NFL.com.
Despite that familiarity between Saleh and Shanahan, Eric Branch of the San Francisco Chronicle said the new hire was not San Francisco's first choice. Rather, he was listed after Gus Bradley and Vic Fangio—the former became the San Diego Chargers defensive coordinator, while the Chicago Bears wouldn't release the latter from the last year of his contract.
Saleh may not have been the top option for the 49ers, but he helped coach a Jacksonville defense that was an impressive sixth in the league in total yards allowed in 2016. What's more, linebackers Paul Posluszny and Telvin Smith each finished with more than 100 tackles during the campaign.
San Francisco's defense needs production like that after a dismal 2-14 finish in 2016.
Branch pointed out the 49ers "allowed the eighth-most yards (6,052) and ninth-most points (480) in league history" and set a league record by allowing a 100-yard rusher for seven consecutive contests. As a result, the 49ers finished dead last in rushing yards allowed in 2016.
Caplan said they'll likely institute a 4-3 defense.
Inman provided a silver lining and noted the 49ers will return a handful of starters who suffered injuries and missed time in 2016, including linebackers NaVorro Bowman and Ray-Ray Armstrong, defensive backs Eric Reid and Jimmie Ward, and defensive tackle Arik Armstead.
Saleh will need all the help he can get from those playmakers as he looks to turn around the defense for the once-proud franchise that will try to avoid a third straight losing season in 2017.