Randy Johnson is retiring after 22 Major League Baseball seasons. The overpowering lefty known as the Big Unit, who last June became the 24th pitcher in MLB history to win 300 games, made the expected announcement Tuesday on a conference call. “I really wanted to go out on my terms,” Johnson said. “I just feel like there's not a lot more for me to do in this game. I just think it's a natural progression when you play this long. Eventually you have to say it's time.” A five-time winner of the Cy Young Award as MLB pitcher of the year, the 46-year-old Johnson accomplished just about everything in his remarkable career. He won a World Series and co-MVP honor, and was a 10-time All-Star. He threw two no-hitters, including a perfect game, and ranks second on the career strikeout list. The 6-foot-10 (2.09-meter) Johnson finishes with a career record of 303-166 and 4,875 strikeouts in 4,135 1-3 innings for Montreal, Seattle, Houston, Arizona, the New York Yankees and San Francisco. His strikeouts are the most by a left-hander and second to Nolan Ryan's 5,714. Johnson overcame four knee operations and three back surgeries to keep pitching at a high level into his mid-40s. Last year he missed more than two months with a strained left shoulder that also had a tear in the rotator cuff. It was the first serious shoulder problem of his career. He returned in late September as a reliever, a role he couldn't see himself embracing in order to keep pitching. Johnson pitched his first no-hitter in 1990, won 19 games with 308 strikeouts in 1993 and led Seattle to its first playoff berth with an 18-2 record in 1995. He finished his 10-year stint in Seattle with a 130-74 record before being traded to Houston in 1998. He signed as a free agent with Arizona before the following season, beginning one of the most dominating runs a pitcher has ever had. Johnson won the Cy Young in each of his first four seasons with Arizona, capturing the coveted pitcher's triple crown in 2002 with a 24-5 record, 2.32 ERA and 334 strikeouts. His most memorable moments were in 2001, when he came out of the bullpen to beat the Yankees in Game 7 of the World Series to give Arizona the title. He went 3-0 in the World Series, sharing the MVP award with Curt Schilling. Johnson pitched a perfect game at age 40 against Atlanta but he didn't have as much success following the 2004 season as injuries began to take a toll. “I never thought I was going to play this long. I'm blessed that I did,” Johnson said. The Big Unit added that he plans to coach someday. He has a one-year service agreement to work in some capacity for Arizona.