Sources: DC Matt Wallerstedt fired

ByJAKE TROTTER
September 18, 2014, 2:00 PM

— -- Texas Tech fired defensive coordinator Matt Wallerstedt after the coach was suspected of being under the influence of an unknown substance while on campus, sources told ESPN.com on Thursday.

Wallerstedt was sent home from the facility Monday, according to a source.

The Red Raiders surrendered 438 rushing yards in a 49-28 loss to Arkansas last weekend, but the team's on-the-field performance was not related to Wallerstedt's dismissal, sources said.

CoachingSearch.com first reported the firing Thursday.

Wallerstedt joined the Texas Tech staff last season, coming over from Texas A&M along with head coach Kliff Kingsbury.

He is expected to be replaced by co-defensive coordinator and linebackers coach Mike Smith, who played for the Red Raiders and graduated from Texas Tech in 2004.

Smith will be Texas Tech's seventh defensive coordinator since 2007.

The Red Raiders are off this weekend before traveling to play Oklahoma State on Sept. 25.