The Seattle Mariners are looking to snap their 20-plus year playoff drought. It is the longest drought in the sport and Seattle is praying for a playoff appearance. However, one has to wonder if they can do more than just sneak into the playoffs. The Mariners upgraded ahead of the MLB trade deadline and appear to be a legitimate threat in the American League.

Let's take a look at 3 reasons Seattle is now a World Series contender.

3 reasons Mariners are World Series contenders after MLB trade deadline

Sneaky good moves

No, this isn't talking about Luis Castillo. That was a good move, but it wasn't sneaky. However, Seattle made a couple of moves that flew under the radar.

The Mariners acquired LHP Matthew Boyd and C Curt Casali from the San Francisco Giants. These acquisitions aren't jaw-dropping by any means. Both Boyd and Casali are both injured at the moment.

Casali is expected to return fairly soon and will be a valuable depth piece at the catcher position. He offers little in the way of offensive prowess, but understands how to handle a pitching rotation.

Boyd isn't guaranteed to return this season. But there is a chance he makes a comeback in September. Adding a talented left-hander like Boyd in the midst of a postseason run would be helpful.

Seattle also acquired Jake Lamb from the Los Angeles Dodgers. Lamb is interesting because he can play third base, first base, and outfield. Versatility is always a plus. Additionally, he tears the cover off of the ball against right-handed pitching.

Lamb once had star potential. Although that never panned out, he could be a key factor for the Mariners down the stretch.

Luis Castillo

Okay, let's talk about Luis Castillo.

Seattle acquired Castillo from the Cincinnati Reds ahead of the MLB trade deadline. The move came as a surprise, as many people expected Castillo to end up in New York or LA. But the Mariners and Reds have a history of dealing with one another. Seattle acquired Jesse Winker and Eugenio Suarez from the Reds over the offseason.

But this Castillo trade was an extremely important one for the Mariners.

Prior to adding the right-hander, they featured a decent rotation. Robbie Ray and Logan Gilbert led the charge, while Marco Gonzalez and Chris Flexen profiled as complimentary options. But is that a World Series contending rotation? Especially given Ray's struggles in 2022?

Probably not.

But Castillo makes the Mariners' depth chart look far more intimidating. We will discuss that more in a second.

On the season, Luis Castillo posted an ERA of under 2.90 with the Reds. His strikeout ability has continuously improved due to a more balanced repertoire. For a while, his only superb pitch was the change-up. But he now has better control of his fastball and can throw other effective breaking pitches on a more consistent basis.

So we know he's a good pitcher. But it is his effect on the entire rotation that puts the Mariners over the top.

Castillo's effect on the rotation

Luis Castillo helps alleviates pressure for the rest of rotation. His presence allows Robbie Ray to settle in as a number 2 option. Ray doesn't have to be the go-to guy anymore. And he will be able to relax and pitch more effectively as a result.

It also effects Logan Gilbert. Gilbert now has two All-Star caliber pitchers ahead of him in the rotation. He can learn from both and settle in as a No. 3 option for the Mariners.

Luis Castillo truly is a game-changer. He will look to help the Mariners reach the playoffs, and maybe even the World Series.