The man in this video — recorded just 5 miles from Nancy Guthrie‘s home — is on the FBI’s radar — TMZ has learned — and the timing of the video is critical.

Law enforcement sources tell TMZ … the FBI is lasering in on the man in the video, who is both wearing and carrying backpacks … right around the time of the kidnapping.

The backpack the man is carrying appears to have reflective straps … similar to the one the apparent kidnapper was wearing as he approached Nancy’s front door. It’s unclear if the reflectors are on the shoulder straps or the side of the backpack.

TMZ broke the story … the backpack seen at Nancy’s house is a Walmart Ozark Trail Hiker, and that has now been confirmed by authorities.

The man in the new video is trying to enter a locked gate, to no avail. He was recorded on a resident’s Ring camera at 1:52 AM.

Now, when law enforcement held a news conference last week, they said Nancy’s Nest camera disconnected at 1:47 AM … and, at 2:12 AM, the camera software detected a person. The video the FBI released of the man approaching Nancy’s door does not have a time stamp.

Sources directly connected to the investigation tell TMZ … that video of the man at Nancy’s door was recorded at 2:12 AM — in other words, he’s the person the software detected.

So, the video of the man with 2 backpacks left that scene at 1:53 AM … BEFORE Nancy was kidnapped. IF he is the kidnapper, he would have had 19 minutes to drive the 5 miles, put on his disguise, and approach Nancy’s door.