Win-win trade as Mariners, Rays make six-player swap

Mariners and Rays involved in first big offseason trade (1:35)

ESPN SweetSpot blogger David Schoenfield breaks down the six-player deal between the Mariners and the Rays. (1:35)

The trade: The Seattle Mariners trade shortstop/outfielder Brad Miller, first baseman Logan Morrison and right-hander Danny Farquhar to the Tampa Bay Rays for right-hander Nathan Karns, left-hander C.J. Riefenhauser and minor league outfielder Boog Powell.

This looks like a good old-fashioned challenge trade, two teams dealing from a relative position of strength to fill obvious holes: The Rays need a shortstop with Asdrubal Cabrera hitting free agency, and the Mariners need to improve a rotation that finished ninth in the American League in ERA and has Hisashi Iwakuma as a free agent.

Miller is a guy I've always liked, a good athlete with some power and speed. His problem was on defense, where he'd boot routine plays, usually with bad throws. The Mariners finally gave up on him as a shortstop when they promoted Ketel Marte late in the season and tried him in the outfield, continuing a bad Mariners experiment of moving middle infielders to the outfield (Dustin Ackley, Nick Franklin).

Here's the thing: Miller didn't look good in the field -- he was never smooth, and sort of flings the ball sidearm to first base -- but his defensive metrics weren't horrible there. In 2014, he rated at minus-3 Defensive Runs and in 2015 he rated at 4 runs below average. Over those years, Ultimate Zone Rating has him at plus-1.6 runs per 150 games, about on par with Jhonny Peralta and Erick Aybar, and nobody is moving those guys off shortstop.

As a Mariners fan who watched quite a bit of Miller, I can see why the Mariners dealt him. His errors also seemed to come at crucial moments, and ninth-inning errors lost a couple of games for the team. But his arm is pretty strong, and strong-armed shortstops are often underrated. The Rays are buying into the metrics more than the eye test; considering this is a team that has historically valued defense, Tampa Bay must be confident he can at least be average-ish at shortstop.

Miller hit .258/.329/.402 in 2015, a line that shoots up to .266/.350/.453 against right-handers. That's well above-average production for a shortstop. Trouble is, he hit .234/.264/.252 against southpaws, with only two doubles and no home runs in 111 at-bats, after hitting .170 against lefties in 2014. So there's some strong evidence that the lefty-hitting Miller needs a platoon partner, maybe Tim Beckham, who slugged .462 against lefties in 2015 and started 22 games at shortstop.

Karns went 7-5 with a 3.67 ERA in 26 starts as a rookie. He's not young, however, as he'll be entering his age-28 season, having begun his pro career late because of a torn labrum suffered in college and then battled control issues in the minors. With Chris Archer, Jake Odorizzi and former Mariner Erasmo Ramirez fronting the rotation, plus, one hopes, full seasons from Drew Smyly and Matt Moore and the possible return of Alex Cobb, the Rays had depth to deal. Karns throws a four-seam fastball up in the zone that isn't overpowering (average velocity 91.8 mph), and also throws a curveball and changeup. Scouts consider the curve his best pitch, and batters hit only .170 against it in 2015.

Karns averaged 8.9 strikeouts per nine innings with the Rays in 2015 and 10.3 per nine in his minor league career, so he always has been able to put away batters. The Rays didn't push their starters deep into games, so Karns went seven innings only three times, but he also gave up two runs or fewer in 20 of his 26 starts.

In the end, I see two solid but flawed players, neither likely to break out into a star but useful regulars. Karns is the little bigger risk because of health issues in his past and the concern his control suddenly regresses again (plus, Tampa Bay pitching coach Jim Hickey is considered one of the best in the business).

The other guys are mostly filler. Morrison is no longer an adequate starting first baseman, with an OPS+ of under 100 in three of the past four seasons. Farquhar is an undersized righty who had a very good 2014 (like the rest of the Seattle bullpen) and a very bad 2015 (like the rest of the Seattle bullpen). He has a decent arm and is the kind of reliever the Rays like to take chances on.

Riefenhauser is a lefty with LOOGY stuff who has put up good numbers in the minors but has been roughed up in 20 major league innings. Powell is sort of an interesting guy, and not just for the blasphemous name -- there can, after all, be only one Boog Powell, even if this Boog got the nickname because the original was his grandfather's favorite player.

A 20th-round pick by the A's in 2012 out of junior college, he had a 50-game amphetamine suspension in 2014 but reached Triple-A last year with Tampa at age 22 on the strength of his hit tool, speed and on-base skills. He has little power, with only six career home runs in the minors in more than 1,000 at-bats, but he hit .295/.385/.392 between Double-A and Triple-A in 2015. His chance to become a regular -- the Mariners need a center fielder -- will depend on his defense and ability to keep hitting for a high average. I do wonder how fast he really is, however, as he has been a poor percentage base stealer in the minors (18-for-32 in 2015). So while he draws comparisons to Billy Burns of the A's, he looks more like a fourth outfielder to me.

Anyway, a fun trade to kick off the offseason. We don't usually see these kinds of deals much anymore, so kudos to Jerry Dipoto and Matt Silverman for one that seems to make sense for both clubs.