Maybe the thing that has distinguished this offseason in baseball is optimism. Hope springs, etc. This isn't just the normal wave of good feelings many of us feel about our favorite team as Spring Training approaches.
General managers see opportunity in a landscape in which 18 of 30 teams have been to the postseason at least once the past three seasons. If every other team is doing it, why can't we?
This is the way it ought to be, right? So the Rangers improve by 21 games and return to the postseason in 2015. The Astros get 16 games better, the Blue Jays 10. Both end a lengthy playoff drought.
Almost every team envisions a path to the postseason. In 2015, five of the eight teams that got to a Division Series had missed the playoffs altogether in '14.
There could be more of that in 2016. For instance, two of the American League's last-place teams in 2015 -- the Tigers and the Red Sox -- have improved so much that it wouldn't even be a surprise to see them win their division.
For that reason, they're not eligible for this list. Rather, let's take a look at six clubs that are a bit more in the long-shot category but still seem nicely positioned for a big turnaround:
1. Mariners (76-86 in 2015)
Key additions: LF Nori Aoki, CF Leonys Martin, 1B Adam Lind, C Chris Iannetta, RHP Wade Miley, RHP Nathan Karns, RHP Steve Cishek, RHP Joaquin Benoit, 1B Dae Ho Lee, C Steve Clevenger and manager Scott Servais.
No general manager overhauled his club as dramatically as the new guy in Seattle, Jerry Dipoto. Oh, and did we mention he hired a new manager? The Mariners will have so many new faces that it may take half a season to figure out how the pieces fit.
This is how the Mariners can make the postseason:
• Get big seasons from their superstars, second baseman Robinson Cano and ace Felix Hernandez. With every potential contender, this is the starting point.
• Get solid years from third baseman Kyle Seager, right-hander Hisashi Iwakuma and young shortstop Ketel Marte.
• Have a competitive rotation behind Hernandez and Iwakuma. That means Miley, Taijuan Walker, James Paxton and Karns have to be good. This isn't reaching. They're all capable. They can mean the difference between making and missing the postseason.

2. A's (68-94 in 2015)
Key additions: 2B Jed Lowrie, 1B Yonder Alonso, LHP Rich Hill, RHP Marc Rzepczynski, RHP Liam Hendriks, RHP Ryan Madson, RHP John Axford and RHP Henderson Alvarez.
A's president of baseball operations Billy Beane had a quieter offseason, but nevertheless an aggressive one. He reworked and upgraded his bullpen and the left side of his infield, and Oakland is getting important players back from the disabled list.
This is how the A's can make the postseason:
• Have good health. The A's have been decimated by injuries at times the past couple of seasons. If closer Sean Doolittle, left fielder Coco Crisp and right-hander Jarrod Parker are out there, Oakland has a chance.
• Have the new bullpen perform as well as it is capable of.
• Have shortstop Marcus Semien cuts those 35 errors in half to become the player Beane projected him to be a year ago.

3. D-backs (79-83 in 2015)
Key additions: RHP Zack Greinke, RHP Shelby Miller and SS Jean Segura.
The D-backs are going for it. With first baseman Paul Goldschmidt and center fielder A.J. Pollock in the prime of their careers, Arizona executives didn't want to see an opportunity pass them by. Only the Rockies scored more runs in the National League last season, and the D-backs have an impressive array of young pitchers. Now they have a solid one-two punch at the front of the rotation.
This is how the D-backs can make the postseason:
• Get 60-plus starts from Greinke and Miller.
• Get rotation contributions from top prospects Archie Bradley and Braden Shipley.
• Have their bullpen arms remain healthy.

4. Marlins (71-91 in 2014)
Key additions: LHP Wei-Yin Chen, RHP Edwin Jackson, manager Don Mattingly and hitting coach Barry Bonds.
The Marlins are one of the few teams with two superstars -- right fielder Giancarlo Stanton and right-hander Jose Fernandez. All they haven't been able to do is see a lot of them on the field together. In the end, Miami's primary goal is to get healthy seasons from them. If that happens, a lot of good stuff may follow.
This is how the Marlins can make the postseason:
• Have stability. No managerial changes. No crushing injuries. No drama.
• Get solid seasons from left fielder Christian Yelich and center fielder Marcell Ozuna.
• Have fourth and fifth starters emerge from a group that includes right-hander Jarred Cosart and left-handers Justin Nicolino and Adam Conley.

5. White Sox (76-86 in 2015)
Key additions: 3B Todd Frazier, C Alex Avila and 2B Brett Lawrie.
General manager Rick Hahn has pretty much remade his club the past two offseasons, aggressively adding talent from both free agency and trades. In ways large and small, he has done his job.
This is how the White Sox can make the postseason:
• Have Lawrie adjust to second base and settle in offensively.
• Have first baseman Adam LaRoche produce more than he did in 2015, when he hit .207.
• Have former high Draft choices Carlos Rodon and Erik Johnson fill in the rotation productively behind Chris Sale, Jose Quintana and John Danks.

6. Rays (80-82 in 2015)
Key additions: DH Logan Morrison, SS Brad Miller, LF Corey Dickerson, DH Steve Pearce and RHP Danny Farquhar.
The Rays have been 25th and 27th in runs the past two seasons and wasted a lot of quality pitching. That's what this offseason was about, and president of baseball operations Matt Silverman succeeded in upgrading the club in several others.
This is how the Rays can make the postseason:
• Get good production from left fielder Desmond Jennings and right fielder Steven Souza Jr. without injury.
• Have third baseman Evan Longoria and first baseman James Loney produce the way they have most of their careers.
• Have Miller establish himself once and for all in the big leagues at shortstop.
• Have right-hander Alex Cobb return from Tommy John surgery sometime during the season and make a solid rotation even better.