The Mariners Swap Luis Castillo For Sean Murphy In This MLB Mock Trade That Could Revive Their Fantasy Value

We are now getting deep into the MLB season, with the All-Star Game just over a month away and the MLB Trade Deadline less than two months away on August 3. We are going to start seeing some big trades that will have a significant impact on your fantasy baseball league.

While we often focus on buyers and sellers, sometimes two buyers or two sellers can make a deal with each other in an attempt to benefit both teams on the same timeline. The two first-place teams we could see striking a deal are the Seattle Mariners and the Atlanta Braves.

The Mariners have run a six-man rotation for much of this season, with Luis Castillo being the weakest link. However, he's also making more than $24 million per year, and they are on the hook for him through 2028. They are going to look to move him before the deadline if possible.

If there is a GM who loves to take shots on once-great aging pitchers that he can buy low on, it's Alex Anthopoulos. The Braves just so happen to have some players that they could stand to move on from, too.

Atlanta Braves - Seattle Mariners Mock Trade

Atlanta Braves Receive

RHP - Luis Castillo

Seattle Mariners Receive

C - Sean Murphy

SS - HS Kim

Fantasy Impact

Castillo is in need of a fresh start. He's currently sitting at 2-5 with a 5.16 ERA, which is a career worst. Only once in his career has he had an ERA over 4.00, and that was back in 2018 when he finished with a 4.30 ERA. His K/BB is also way down at 2.7. Things are not going well for him this season.

Struggling players tend to thrive when they make the move to Atlanta and get their careers back on track. We've seen it time and again with this team. It's not a lock that he would pitch better with the Braves, but it would at least give fantasy owners hope for a turnaround, and there is real reason for that hope.

While we expect him to be fazed out of the rotation in Seattle as we get closer to the playoffs, he would be a much more important piece for the Braves, who have been ravaged by injuries to their pitching staff this season. That should at least stabilize his fantasy value.

Sean Murphy has to be considered a bust in Atlanta. He's another player who could use a fresh start. He's currently injured, but is projected to be fully recovered from his finger injury before the trade deadline.

It has become clear that trading Williams Contreras for him was a mistake, but he can still carve out a long-term role in Seattle behind Cal Raleigh. Raleigh is also injured currently, and if they added Murphy, he could also serve as a DH to keep him healthy. Like with Castillo, fantasy owners will have to hope something clicks with a new team.

Kim is essentially a throw-in for financial purposes. Nevertheless, it would be much easier for him to carve out a role in Seattle than in Atlanta at this point. The Braves are deep and have an elite offense.

Seattle is dealing with injuries to their infield and has scored 59 fewer runs than Atlanta. He would be much more valuable there, both at the plate and on the field, if he could get consistent play to help him get back on track.

Why The Trade Makes Sense For The Atlanta Braves

Atlanta needs starting pitching depth and has not been shy when it comes to rejuvenation projects. The emergence of Drake Baldwin has made it abundantly clear that the Sean Murphy contract extension was a mistake. Even though they would be taking on Castillo through 2028, they would be moving off Murphy's $15 million per year through 2028 as well. They need the pitching more than an oft-injured, over-priced backup catcher.

Why The Trade Makes Sense For The Seattle Mariners

Murphy has shown upside at the plate that they will look to unlock, and he's a strong defensive catcher, which they need. He's also a few years younger than Castillo. This is a case of two teams moving off an overpaid player in an effort to change things up, and hope to boost their roster in a more needy area.

They would be taking Kim to free the roster spot for the Braves so their GM can save face for giving him an inexplicable $20 million deal. Nonetheless, he's on an expiring contract, and they'll save a lot more than they'll be taking on. If he doesn't pan out, they can cut him with less scrutiny than the Braves.

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This article was originally published on www.si.com/onsi/fantasy as The Mariners Swap Luis Castillo For Sean Murphy In This MLB Mock Trade That Could Revive Their Fantasy Value.

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This story was originally published June 10, 2026 at 12:16 PM.