[1] As a junior in 1955, head coach Bud Wilkinson moved him to center, which became his signature position, while also playing linebacker.
In the 20–0 victory over the University of Texas, he had 27 tackles and 3 interceptions, prompting Wilkinson to call it "the single greatest game ever played by an Oklahoma defender".
[2] As a senior in 1956, he finished fourth in the Heisman Trophy voting (very high for a lineman), behind his third place teammate, Tommy McDonald, and winner Paul Hornung of Notre Dame University.
After the 1959 season, Tubbs planned to retire, so the 49ers left him off their list of players who were exempt from the 1960 NFL Expansion Draft.
In the 4th game of the 1960 season, Tubbs became the first player in franchise history to start at the middle linebacker position on a regular basis, finishing with 149 tackles (48 solo).
Tubbs was an impact player on those early Cowboys teams and also rated among the top middle linebackers in the NFL.
In 1966 he retired and was working for the Dallas Federal Savings and Loan Association, but was lured back by Tom Landry to play behind Lee Roy Jordan for one more year.
The following year (1967), Landry sensing that the Cowboys had a real chance at a championship, wanted to have Tubbs as insurance in the event Lee Roy Jordan should be injured.
He came back again, but didn't play a single down while serving as a player-coach, hence he was on the roster and in uniform for the 1967 Ice Bowl championship game against the Packers.