Mariners #4 RF: Leon Roberts – 9.0 fWAR
Yup. Leon Roberts was the first Mariners player to hit .300 or better. The team started in 1977, and the best hitter on the team that year was the previous right-fielder, Leroy Stanton. He would hit .275 and see Roberts take the role of RF in 1978 as Stanton struggled.
Roberts had been with the Tigers and Astros for two years apiece and came to Seattle in 1978. He would actually have a fantastic two-year stretch for the Mariners, with a 4.1 fWAR that season and a 3.4 the next year. He would only play one more year with the Mariners, before bouncing around to the Rangers and Royals before retiring at the end of the 1984 season.
1978 was special though. He put up an incredible 145 WRC+, hitting .301/.364/.515, striking out a minuscule 9.8% of the time. Add to that 22 HR, 78 R, and 92 RBI, and you can see why it ranks as one of the best offensive seasons outside of the main guys that frequent the leaderboard.
He dropped down a bit in 1979, and even further in 1980. It was still enough to launch him into the top-5 all-time for Mariners right fielders. He would’ve been third prior to 2021, but was passed by the Mariners current guy that mans the position.