Showers is a 2010 graduate of Shoemaker High School in Killeen, Texas.
He played for Texas A&M University during the 2011 season, serving as a reserve to Ryan Tannehill. The next year, he was the backup to eventual Heisman Trophy winner Johnny Manziel. In June 2013, he earned a bachelor's degree from Texas A&M University.
He transferred to the University of Texas at El Paso for the 2013 season, and was named the starter. Although he missed the last 5 games due to injury, he still managed 1,263 passing yards, 11 touchdown passes, 4 interceptions, 195 rushing yards and 4 rushing touchdowns. The next year, he started all 13 games, registering 1,858 passing yards, 12 touchdown passes, 6 interceptions, 312 rushing yards and 4 rushing touchdowns.
On May 9, 2015, Showers was signed as an undrafted free agent by the Dallas Cowboys. Although he passed for 125 yards, one touchdown and one interception in preseason, he made the coaches take notice with his special teams play and versatility on the scout team. On September 5, he was waived and signed to the practice squad two days later. On December 25, he was promoted to the active roster along with defensive tackle Casey Walker, after the Cowboys placed tight end Gavin Escobar and quarterback Tony Romo on the injured reserve list. He was declared inactive in the last 2 games.
In 2016, he moved up on the depth chart when backup quarterback Kellen Moore broke his right tibia during the first week of training camp and the Cowboys couldn't reach an agreement with the Cleveland Browns to trade for backup Josh McCown.
After Moore's injury, he competed with rookie quarterback Dak Prescott for the backup job behind starter Tony Romo. Several reports from August, indicated that Showers outperformed Prescott, showing greater accuracy and a quicker release in training camp. However, the Cowboys coaching staff made the decision to start Prescott in the team's preseason opener at the Los Angeles Rams. Working with the Cowboys' first-team offense, Prescott completed 10 of 12 passes for 139 yards and two touchdowns in one half of action. In that game Showers had a notable 45-yard pass to Vince Mayle, while escaping a certain sack, although Dallas would lose the game 28-24.
After starting quarterback Tony Romo suffered a vertebral compression fracture during the first quarter of the Cowboys' Week 3 preseason game against the Seattle Seahawks, in light of Romo's projected 8- to 10-week recovery time, Prescott was named the starter for the beginning of the 2016 season. For the backup quarterback position, the Cowboys wanted to pair Prescott with a veteran, so they released Showers on September 4 to make room for Mark Sanchez, signing him to the practice squad the next day. On October 7, it was reported that Showers would be switching positions from quarterback to strong safety, in order to give him a better chance to make the team. He signed a reserve/future contract with the Cowboys on January 16, 2017.
On September 2, 2017, Showers was waived by the Cowboys and was signed to the practice squad the next day. He was released on September 12, 2017 but was re-signed a week later.