Nolan's agent, Bob Lamonte, didn't return a telephone call and an e-mail
Nolan, 45, is the son of former 49ers head coach Dick Nolan.
A former defensive coordinator with the New York Giants, Washington Redskins and New York Jets, Nolan coached the NFL's sixth-ranked defense last season.
Baltimore (9-7) ranked sixth in scoring defense and eighth against the run, scoring seven touchdowns.
In 2003, the Ravens ranked third in total defense, first in sacks (41) and second in takeaways (41).
The 49ers have already scheduled Tennessee Titans offensive coordinator Jim Schwartz, a former Ravens assistant, for a Friday interview, and interviewed Titans offensive coordinator Mike Heimerdinger earlier this week.
York and other 49ers team officials met with New York Giants defensive coordinator Tim Lewis earlier Wednesday, too.
The 49ers have also interviewed New England Patriots defensive coordinator Romeo Crennel, who has been dubbed the leading contender for the Browns' head coaching vacancy.
San Francisco plummeted to a franchise-worst 2-14 last season and fired coach Dennis Erickson and dismissed general manager Terry Donahue. The 49ers have the top overall pick in the draft after defeating the Arizona Cardinals twice for their only two wins.
The Ravens are poised to replace Nolan if he leaves, and would likely promote defensive line coach Rex Ryan to coordinator.
"We've dealt with succession a lot," Baltimore general manager Ozzie Newsome said. "From Shannon Sharpe to Todd Heap, from Rod Woodson to Ed Reed, from Sam Gash to Alan Ricard, from Marvin Lewis to Mike Nolan, from Steve Shafer to Donnie Henderson, we deal with succession all the time.
"You know how good the people we've been able to bring in before, but we can still attract the same type of people."
As well as a being a long time contributor to RavensInsider, Aaron Wilson writes for the Carroll County Times in Westminster Maryland.
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