49ers starting strong safety Malik Mustapha apparently tore his ACL in the 49ers’ regular-season finale a few months ago and is not expected to be ready for the start of the upcoming regular season according to ESPN’s Adam Schefter.

Which means the 49ers knew about Mustapha’s injury before the draft, so at least they’re not caught off guard. It’s hard to fathom how the media didn’t learn about this injury until now. You’d think the 49ers would have been more transparent. Perhaps they didn’t want people to know about Mustapha’s injury until they could draft a potential replacement while he’s out.

And in Round 5 with pick No. 160, the 49ers took Kansas State safety Marques Sigle. Maybe he will fill in for Mustapha while he’s out. Or, maybe the replacement will be third-year safety Ji’Ayir Brown, who played well as a rookie but struggled last season.

Mustapha was one of the 49ers’ few bright spots on defense last season. He was by far their most violent hitter considering Dre Greenlaw missed almost the entire season with a torn Achilles. Mustapha seemed like a player who was poised to make a big leap in his second season.

Now, Mustapha most likely will miss OTAs, minicamp and training camp, which means it will take him a while to get into football shape even after he has been cleared to return to the field.

What a sobering report. I still don’t understand how we’re just learning about this.