Source: 49ers look at Perry Fewell

The season just ended, and Perry Fewell has three teams interested in him.

The San Francisco 49ers have asked the New York Giants for permission to interview the rising defensive coordinator, according to a league source.

On Monday, the Cleveland Browns -- who fired Eric Mangini on Monday -- and the Carolina Panthers -- who let John Fox go on Friday -- submitted interview requests to talk to Fewell according to a source.

The 49ers are looking for a replacement for Mike Singletary and have also requested permission to interview Oakland Raiders offensive coordinator Hue Jackson.

Raiders senior executive John Herrera confirmed the request that was first reported by ESPN NFL Insider Adam Schefter.

"Al is happy for Hue," Herrera said. "He would never stop Hue Jackson from an opportunity to coach. He believes in diversity."

The Raiders fired coach Tom Cable on Tuesday night.

A league source told Schefter on Monday that the 49ers are still targeting Stanford coach Jim Harbaugh. A decision on whether Harbaugh will remain with the Cardinal is expected this week.

Giants general manager Jerry Reese said he will not prevent any assistants from interviewing for higher positions.

"We don't want to hold anybody back," Reese said. "We like our coaching staff. Everybody gets evaluated. I get evaluated, the coaching staff, our players get evaluated. If guys get an opportunity to move on to a better opportunity, we are happy for them if that comes along, but we like our coaching staff right now."

Ohm Youngmisuk covers the Giants for ESPNNewYork.com. You can follow him on Twitter.