He played college football at the University of Oregon.
Mike Gaechter was signed by the Dallas Cowboys in 1962 as an undrafted free agent and became the starting left cornerback as a rookie.
In that season, the Cowboys became the first NFL team in history to produce two 100-yard plays in the same game: a 100-yard interception return for a touchdown by Gaechter (a team record) and a 101-yard kickoff return for a touchdown by running back Amos Marsh.
His interception return was a franchise record that was broken by Bryan McCann 48 years later in 2010.
Although he had a track background, he was a punishing hitter so he was switched to strong safety in 1963, where he earned the reputation as a feared defensive player in the Cowboys secondary.
His late hit in the end zone that upended the Packers’ Boyd Dowler after a touchdown reception in the third quarter of the 1966 NFL Championship Game, caused Dowler a shoulder injury and allowed the seldom-used Max McGee to star in Super Bowl I two weeks later.
Gaechter had been a mainstay on the Cowboys defense for most of the 1960s, but he ruptured his achilles tendon in the 1969 Playoff Bowl against the Los Angeles Rams.
Mike never fully recovered, finishing with 8 seasons and 21 interceptions (13th in club history) during his time in Dallas. He also has two of the five longest interception returns in team history (100 yards and 86 yards in 1963 against the Washington Redskins).
In 1970, Cornell Green moved from cornerback to strong safety to replace Gaechter who was placed on the injured reserve list.
After sitting out the entire season, he was traded to the Washington Redskins for a conditional draft choice on July 20, 1971.
Gaechter was released on August 11, 1971, before the start of the season. he died August 17, 2015 at age 75.