What's the impact of the Luis Castillo trade?

The Mariners swung a blockbuster trade with the Reds for right-hander Luis Castillo on Friday night, sending four players -- including three of their top five prospects -- to Cincinnati to acquire the 29-year-old, who was widely considered to be the best pitcher available.

The deal not only improves Seattle’s postseason chances as it looks to end its 20-year drought -- the longest active playoff drought in the four major North American professional sports -- but also could have a wide-reaching impact on the rest of the trade market.

With three days to go before Tuesday’s 6 p.m. ET Trade Deadline, let's look at six major questions stemming from the Castillo trade.

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1) Are the Mariners a postseason lock?
Through Friday, FanGraphs put the Mariners’ postseason odds at 76.7%, second to the Blue Jays (96.3%) among teams in the AL Wild Card picture. Dan Szymborski's ZiPS projection system bumped the Mariners' postseason chances up to 84% after the trade. They still aren’t a lock to make the playoffs with the AL West crown likely out of reach and so many teams bunched together in the AL Wild Card race, but this trade is a step in the right direction as Seattle looks to solidify its hold on one of the Wild Card spots.

2) What does the AL Wild Card picture look like now?
The race for the three AL Wild Card spots is incredibly close, with the Blue Jays, Mariners, Rays, Guardians and Orioles all separated by four games or fewer and the Red Sox and White Sox in the mix as well. If Toronto and Seattle continue to separate themselves from the pack, five teams could be vying for one Wild Card spot.

3) What moves can other AL Wild Card contenders make to counter?
The Blue Jays have the motivation and the prospects to make a big trade for a much needed starting pitcher -- MLB.com’s Jon Paul Morosi recently mentioned the Rangers’ Martín Pérez as a potential fit if Texas makes him available -- and the injury-decimated Rays are likely to seek a bat. (Perhaps Cubs catcher Willson Contreras?) The White Sox and Guardians are in the market for pitching help, while the Orioles might opt to sell despite their surprising success this season. If the Red Sox go for it, Nats first baseman Josh Bell would make sense, though Boston might find itself in the seller category as well.

4) How does this shape the markets for other top starters?
The demand for starting pitchers already far outweighed the supply in this summer’s trade market, and the crop of available arms has only been diminished further. The Yankees, White Sox, Twins, Cardinals, Dodgers, Blue Jays, Brewers and Phillies are believed to be among the contenders seeking rotation help. With Castillo off the board, the spotlight is now on the A’s Frankie Montas, the second-best pitcher on the market after Castillo. Many of the teams that were in on Castillo could shift their focus to Montas (the Yankees already have) driving up his price tag.

We could also see increased demand in secondary options such as the Reds’ Tyler Mahle, the Angels’ Noah Syndergaard and the Pirates’ José Quintana. And with three days left before the Trade Deadline, the chances have increased that at least one long-shot starting pitcher trade candidate -- the Giants’ Carlos Rodón, the Marlins’ Pablo López and the Red Sox’s Nathan Eovaldi -- will draw an offer that’s too good to turn down.

5) How does this impact the Soto market?
The Mariners were said to be one of the teams aggressively pursuing Nationals superstar outfielder Juan Soto, but after parting with three of their top five prospects in the Castillo deal, it will be difficult for the M's to come up with an offer that satisfies Washington. ESPN’s Jeff Passan reported that the Nats have been asking for five or six top prospects in exchange for Soto. Per MLB Network insider Jon Heyman, the Padres, Cardinals and Dodgers are the three teams at the forefront of Soto trade talks, with the Rangers involved in some capacity as well.

Los Angeles was also one of the favorites for Castillo, but with the right-hander no longer in play, the club could have more motivation to go after Soto rather than pursuing one of the other available starting pitchers, knowing its rotation will receive a boost from the returns of Dustin May and Walker Buehler from the injured list prior to the postseason.

6) Could the Mariners still make other moves?
Seattle improved its offense with the addition of Carlos Santana earlier in July and has now has addressed its rotation with its trade for Castillo, but you can never count out general manager Jerry Dipoto when it comes to the trade market. If the Mariners do make another deal, it would make sense for the club to target a reliever after Diego Castillo just went on the IL. The club also could use an offensive upgrade at second base over Adam Frazier (77 OPS+) and Abraham Toro (61 OPS+), but the options are limited.