A Juco from Highland Community College. I guess this is a sign that Tanner's career may be over, and they fee the need for another upperclassman at TE. He'll be a Junior.
New verbal per 247Sports, where he is rated 75. He also had an offer from Western Illinois.
Video Highlights at Hudl.
Rivals has him at 6'5" 250, 4.75, which is good speed for that size. They show an offer from Western Ky.
Scout doesn't list him.
ESPN page.

It also mentions that 21 TEs have been recruited so far from Juco. That seems like a lot for one year, and may indicate an increasing need for them.

Brennan is a very interesting guy.  Accoding to JC Gridiorn, he is rated # i.  See article "Tight Ends Class is Loaded" at bottom of Rivals rating of this lad.   

6'-3", 187 lbs in HS.  That's an impressive amount of bulk to add in just 2 years.  TE definitely seems like a position of need next year, but I do like what we've seen from Mangen.

Three TEs will be gone next year, Hill, Talbert, and Asher. In theory that leaves:
Troy Mangen 6'5" 252 - True Soph - played this year
Mason Morgan 6'6" 232 - Redshirt Fr - Redshirted this year
Davon Henry 6'3" 240  - Redshirt Soph - Held out with injury this year, redshirted last year
John Tanner 6'4" 255  - Redshirt Soph - Injured both of last two years, career may be over
Devin Saunders 6'5" 245 - Redshirt Senior - walkon this year, didn't play
Connor Brown - 6'6" 225 - True Freshman
Kyle Kuhar - 6'4" 245 - True Freshman
Brennen Borland 6'5" - Incoming JUCO, Jr

There are also some DEs that can/have plaed TE:
Casey Sayles - 6'3" 263 True Sophomore
Trent Smart - 6'3 237 Redshirt Freshman

Somewhere in this group they need to find 2-3 of these that can play. I can see why they decided to  bring in a Juco, though.