In his final 12 appearances of the season, Mason struck out 21 in 20 innings, allowing just five runs. Overall, he finished with a 3-0 record, 5.52 ERA and 29 punchouts in 291/3 innings, including three postseason innings.
"The first month it took a little getting used to, but I got pretty good at it," Mason said of throwing in relief. "Toward the end of the season I was pitching more and my arm was reacting well. I felt pretty strong."
The 6-foot-3, 190-pound hurler pitched effectively in two appearances in the Pioneer League Playoffs, retiring nine of 11 batters he faced and striking out five.
Although Grand Junction lost the hotly contested opening round-series, falling victim to the Ogden Raptors in three games, Mason flourished in pressure situations. He stranded a couple of inherited runners in Game 2 of the series, paving the way for a come-from-behind Grand Junction win, the franchise's first playoff victory.
Ed Santa, the Rockies scout who signed Mason, said the organization is pleased with Mason's progress.
"He's a left-handed pitcher who can throw the ball up to 92. 93 miles per hour, and he always throws strikes," Santa said. "With his potential, we think that he's a major league prospect."
Santa said Mason's willingness to succeed could eventually land him in the major leagues.
"When you get to the minor leagues, all of the guys are good," the veteran scout said. "What separates the guys is their makeup and their ultimate competitiveness and desire to be in the big leagues and be a successful pitcher.
"Mike's going to be a kid who will do whatever we tell him to do to get to the major leagues."