MTSU president Sidney McPhee said in a statement that Conference USA's recent additions of Jacksonville State, Liberty, New Mexico State and Sam Houston State will help stabilize the league.
Later in the day, C-USA commissioner Judy MacLeod issued a statement saying Western Kentucky "remains a tremendous fit culturally, geographically, academically and competitively" and that "we look forward to their continued membership in Conference USA."
The Mid-American Conference on Wednesday said it was not considering expansion plans at this time.
Conference USA has lost nine current members in the latest round of realignment. Six schools -- Charlotte, Florida Atlantic, North Texas, Rice, UAB and UTSA -- are set to join the American Athletic Conference, while Marshall, Southern Miss and Old Dominion are headed to the Sun Belt.
"With the addition of four new members, C-USA offers a strong footprint in the South and Southwest, providing opportunities to develop new regional rivalries, while staying connected to traditional opponents that our fans want," McPhee said in the statement. "Building on the conference's storied history of success, I believe our continued affiliation offers our Blue Raider community the greatest opportunity for success and should enhance our fan engagement. Working with our four remaining members, as well as our new partners, Conference USA is poised to rebrand itself as a premier conference in the Group of 5."
Middle Tennessee joined Conference USA from the Sun Belt in 2014.
"At nine institutions strong, we are excited for our future and will continue to evaluate the national landscape moving forward," MacLeod said in her statement.
The commissioner also said C-USA would be "deliberate and strategic in exploring any potential additional expansion."