Failure to Deploy

Sometimes, in retrospect, the answer is obvious. The Seattle Mariners of the late 1990s were one of the most talent-loaded teams in baseball history in terms of front-line stars: four immortals (Ken Griffey, Alex Rodriguez, Randy Johnson, and Edgar Martinez) one significant star (Jay Buhner) and a couple of productive regulars (Jeff Fassero, Jamie Moyer, Paul Sorrento). Yet from 1996-2000, they made it out of the first round of the playoffs only once (losing the ALCS in 2000), and posted two losing records. Only when Griffey, A-Rod and Johnson were all gone (along with Fassero and Sorrento) and Buhner finished would the team build a 116-win juggernaut in 2001, in part with the pieces acquired for Johnson and Griffey.
Injuries were part of that story (Randy Johnson started just 8 games in 1996, Buhner missed half the season in 1998 and again in 1999), the pitching was chronically thin, especially the bullpen behind the likes of Heathcliff Slocumb, and of course a two-year run of epic bad trades that stripped the team of both young stars and useful role players:

December 1995:
Traded Tino Martinez, Jim Mecir and Jeff Nelson to the New York Yankees. Received Russ Davis and Sterling Hitchcock.
Traded Miguel Cairo and Bill Risley to the Toronto Blue Jays. Received Edwin Hurtado and Paul Menhart.
August 1996:
Traded a player to be named later to the Minnesota Twins. Received Dave Hollins. The Seattle Mariners sent David Ortiz (September 13, 1996) to the Minnesota Twins to complete the trade.
December 1996:
Traded Sterling Hitchcock to the San Diego Padres. Received Scott Sanders.
July 1997:
Traded Derek Lowe and Jason Varitek to the Boston Red Sox. Received Heathcliff Slocumb.
Traded Jose Cruz to the Toronto Blue Jays. Received Paul Spoljaric and Mike Timlin.
August 1997:
Traded players to be named later to the Minnesota Twins. Received Roberto Kelly. The Seattle Mariners sent Joe Mays (October 9, 1997) and Jeromy Palki (minors) (October 9, 1997) to the Minnesota Twins to complete the trade.

But one of the underrated flaws of that team, in retrospect, was the failure to give a longer shot to a talented young player moldering on the team’s bench. Raul Ibanez in 1996 was 24 years old and coming off an age 22 season batting .312/.375/.486 and age 23 season batting .332/.395/.612 in A ball. Over the five seasons that followed – age 24-28, the years that should have been his major league prime – Ibanez would be given 518 plate appearances with the Mariners, just over 100 a year, before leaving for the Royals as a free agent. Ibanez, of course, would go on to stardom with the Royals (he drove in 103 runs in 2002) and return as a free agent after three years there. From age 30-37, Ibanez would bat .290/.351/.489, averaging 97 RBI a year. He’s still playing at 40; at last check, he’s slugging .500 and on pace to drive in 99 runs, although it’s early yet.
To be fair, Ibanez didn’t distinguish himself in his cups of coffee, batting just .241/.295/.383. He would bat .297/.364/.447 and .304/.349/.498 in 1996-97, mostly at AAA Tacoma, and struggle to a .216/.301/.363 line in a half-season’s work in 1998 before spending most of the rest of the period with the big club.
Still, you have to wonder how much worse the Mariners would have done if they’d just slapped Ibanez (or Cruz, for that matter) into the big league lineup in 1996 and left him there to work through the learning curve. Here’s how the team’s endless revolving door of left fielders (including Ibanez as well as Cruz, Rickey Henderson, Stan Javier, Al Martin, Mark McLemore, Brian Hunter, Butch Huskey, John Mabry, Glenallen Hill, Shane Monahan, Rich Amaral, Rob Ducey, Lee Tinsley, Roberto Kelly, Mark Whiten, Darren Bragg, and Alex Diaz) hit over those five seasons:

1996 697 608 155 25 4 23 103 76 67 121 20 7 9 .255 .336 .423 85
1997 665 612 164 34 4 24 84 78 41 133 16 5 13 .268 .314 .454 97
1998 651 608 168 40 4 17 76 76 33 127 10 4 15 .276 .315 .439 91
1999 712 658 158 15 5 12 96 64 41 111 42 7 12 .240 .281 .333 52
2000 762 645 164 23 6 11 117 59 103 108 42 14 12 .254 .356 .360 74
Avg 697 626 162 27 5 17 95 71 57 120 26 7 12 .258 .321 .400 79

(The walks column makes it pretty apparent when Rickey hit town).
Even the 2001 team never really solved the LF problem, splitting time among Martin, McLemore and Javier (combined LF batting line: .256/.350/.364, although they probably contributed more to the team’s historically effective team defense than Ibanez would have), and adding Ruben Sierra and Willie Bloomquist to the mix in 2002 (combined LF batting line: .277/.365/.424) before giving the job to Randy Winn in 2003, then shifting Winn to center to finally install Ibanez in 2004.