When the Seattle Mariners began their first season in April 1977, they were a diverse team still searching for key players to build a future. Julio Cruz came into the picture. Initially signed from the California Angels' farm system, the smooth-fielding switch-hitter was picked by Seattle in the 1976 expansion draft. He gained immediate experience in the majors as a 22-year-old rookie that summer, and the next year, he became the franchise's first regular starting second baseman.

Known affectionately as "The Cruzer" by a growing Pacific Northwest fan base, his value wasn't based on raw power or extra-base hits. Cruz epitomized the dead-ball style speedster of the late 1970s; during his six-and-a-half seasons in Seattle, he was a light hitter with only 17 home runs and a modest .243/.327/307 slash line. Nonetheless, he had exceptional base-running instincts and an innate talent for causing chaos once he reached first base.

Cruz used his lightning-fast speed to solidify himself as the anchor of manager Darrell Johnson’s lineup, constantly challenging opposing catchers with aggressive baserunning. His performance peaked in the 1978 Season, when he raced across the Kingdome’s artificial turf to steal a career-high 59 bases. This breakout established him as an elite baserunner, and he consistently surpassed 40 stolen bases each year for the following four seasons, regularly creating scoring opportunities for a team in need of offensive stability.

Beyond his peak in dynamic base-running, Cruz offered consistent, highly efficient infield play. His soft hands and excellent lateral range contributed to his strong relationship with teammates around second base, making him a beloved clubhouse leader during the team's early years. The end of his notable tenure in Seattle came in June 1983, when the front office traded him to the Chicago White Sox in exchange for infielder Tony Bernazard. Cruz quickly found success in Chicago, becoming a key player that helped the White Sox achieve a 99-win season and win the American League West division.

He finished his Seattle career with 701 hits and 290 stolen bases in 722 games. He held the franchise record for stolen bases for 25 years until Ichiro Suzuki surpassed him in 2008.

Jim Beattie came to the Pacific Northwest with credentials that few of his new teammates could rival. An Ivy League star from Dartmouth, this tall 6-foot-5 right-hander had already achieved baseball's highest honor as a rookie in 1978 by starting and winning Game 5 of the World Series for the New York Yankees. But the intense New York environment changed quickly, and after just two winters, Beattie was traded to the expansion Seattle Mariners in a multi-player deal. He went from the high-pressure spotlight of New York to the challenges of a franchise seeking its identity, moving from a playoff contender to the bottom of the American League.

His initial time on the Kingdome turf was a tough baptism, marked by misfortune and little local support. Beattie faced a difficult 1980 debut, ending with a 5–15 record and a 4.85 ERA. After a similarly tough start in 1981, which included a brief demotion to Triple-A Spokane, he returned to the major leagues with a completely revised approach. Despite continuing to post losing records—a common outcome for a team that often finished last in the division—Beattie quietly became a reliable, intelligent mainstay of the starting rotation.

His major breakthrough as a key pitcher came in a remarkable 1982 season. Over 26 starts, Beattie posted a strong 3.34 ERA, ranking seventh in the American League, and his 140 strikeouts placed him eighth in the league. He combined impressive swing-and-miss ability with effective efficiency, becoming a star attraction for local fans who saw that his talent greatly surpassed his misleading 8–12 record.

That durability reached its peak during the crucial summers of 1983 and 1984. On September 27, 1983, Beattie achieved a historic milestone by pitching a one-hit shutout against the Kansas City Royals—the first in franchise history. He continued with a heavy workload in 1984, pitching 211 innings and completing 12 games. His consistent ability to go deep into games and keep his bullpen fresh earned him top-ten bWAR rankings among American League pitchers in both years, exemplifying a model of stable and focused performance.

After a sharp decline over two injury-plagued winters, Beattie threw his final major league pitch in August 1986. He left with a 43–72 record, 24 complete games, and 563 strikeouts over 944.1 innings.

Before Phil Bradley became an accomplished major-league outfielder, he was already a notable athlete in the Midwest. At the University of Missouri, he excelled as an All-American outfielder and simultaneously was a three-time Big Eight Offensive Player of the Year as a quarterback. After being picked in the third round of the 1981 amateur draft by the Seattle Mariners, he quickly developed his exceptional hand-eye coordination in the minors. By 1983, he had made it to the big leagues, bringing energetic athleticism to a young team eager for talented table-setters.

Bradley’s breakout came during the historic 1985 season, a summer when he produced one of the most explosive individual performances for the franchise that decade. As the team's regular left fielder, his quick wrists and disciplined hitting overwhelmed opposing pitchers. He hit an impressive .300, ranking seventh in the American League, and achieved career highs with 192 hits, 33 doubles, 26 home runs, and 88 RBIs. His standout season included a dramatic walk-off grand slam against the Minnesota Twins on April 13, which led to his first All-Star selection and a 16th-place finish in the AL MVP voting.

He demonstrated how his exceptional performance in the 1986 season relied on selective patience rather than raw power. While his home runs remained steady at 12, Bradley improved his batting average to an impressive .310, placing him eighth in the league. His disciplined approach made him a difficult matchup, drawing 77 walks and achieving a stellar .405 on-base percentage, which ranked among the top ten. Coupled with his 21 stolen bases, he consistently created scoring chances at the top of the order.

In 1987, Bradley had a highly productive summer in the Pacific Northwest, hitting .297 with 14 home runs, 38 doubles, and 101 runs scored. He also showcased his speed by stealing 40 bases, a career high. Despite his popularity and efficiency, the team traded him to the Philadelphia Phillies in December 1987 for a package that included utility player Mike Jackson and outfielder Glenn Wilson. While he continued to perform well with the Phillies, Orioles, and White Sox, Bradley’s prime physically was spent entirely in Seattle.

Bradley compiled 52 home runs, 107 stolen bases, and an exceptional .301/.382/.449 slash line across 607 games in Seattle.

Floyd Bannister had already carried sky-high expectations as the Houston Astros’ number-one overall draft pick in 1976. After two up-and-down developmental seasons in Texas, the Mariners front office made a crucial trade in January 1979 to bring the Seattle-area high school phenom back home to the Pacific Northwest. Stepping directly into the top tier of manager Darrell Johnson’s starting rotation, Bannister instantly provided a struggling, third-year expansion roster with a dynamic power arm that commanded respect around the league.

Bannister’s four-year residency in the Emerald City was defined by a heavy, rising fastball and a sharp, devastating curveball that routinely baffled opposing lineups. Because the early Mariners rosters were plagued by a lack of run support and defensive inconsistencies, his surface win-loss numbers suffered, resulting in a deceptive 40–50 record across his tenure. However, advanced metrics revealed a far different reality; Bannister was a highly competent, high-volume anchor who consistently chewed up frames in the hitter-friendly Kingdome, logging back-to-back seasons of at least 217 innings pitched while maintaining a stingy 3.75 ERA that kept a young team afloat.

His individual masterpiece arrived during the historic 1982 campaign, a summer when his raw potential translated into era-defining dominance. Bannister caught fire under manager Rene Lachemann, taking the ball in 35 high-intensity starts and throwing 247 masterful innings. He weaponized his signature swing-and-miss stuff to lead the entire American League, racking up a career-high 209 strikeouts and securing the league's strikeout crown. That spectacular performance earned him a well-deserved selection to his first and only Major League Baseball All-Star Game, validating his standing as one of the premier left-handed power arms in the junior circuit.

While his high-strikeout efficiency made him a marquee attraction for local fans, the financial realities of a small-market expansion club ultimately cut his hometown stay short. Following his spectacular, award-winning 1982 showcase, Bannister tested the open market as a highly coveted free agent, parlaying his elite Seattle resume into a lucrative multi-year contract with the Chicago White Sox. He would immediately help guide Chicago to a division title the following winter and embark on a highly successful 15-year big-league career across multiple organizations.

Bannister walked away from the Kingdome mound having logged 118 appearances for the organization, accumulating 564 strikeouts and 24 complete games.