Catcher Welington Castillo’s decision Monday to decline his $7 million option for 2018 and become a free agent wasn’t a surprise, and it probably won’t have a huge impact on the playing field.

The 30-year-old backstop hit .282 with 20 homers in 96 games. He threw out 49 percent of would-be basestealers, the best among the 29 qualifiers in the majors, and had a 5.60 catcher’s ERA, the second worst mark among MLB qualifiers.

By all accounts, he was a solid player and a solid guy and he did his job fairly well – meaning the $6 million contract he signed last December worked out swimmingly for both parties, because now he should get a multi-year deal on the open market. But he may have also helped the Orioles going forward, and not just because his presence made it easier to give prospect Chance Sisco more seasoning.

Castillo’s 2017 contract, and subsequent play during that contract, is significant for two reasons.

One, it further emphasizes Baltimore as a great place for hitters to re-establish themselves for a year. Add Castillo to the recent list of position players, along with Nelson Cruz, Nate McLouth, Chris Davis and Mark Trumbo, who have had strong walk seasons while playing for the Orioles and playing half their games in cozy Camden Yards.

As frustrating as it is that no quality starters want to pitch there, especially if it is on a one-year deal to re-establish themselves, the opposite can be said for hitters. And, so, the Orioles can continue that sales job this winter when a seasoned hitter is looking for a reasonable “pillow contract.”

Perhaps the most significant aspect of a successful pact with Castillo, however, is that it was the Orioles’ first toe-dip into the opt-out-clause waters.

OK, so Dan Duquette, the club’s executive vice president, doesn’t view opt-outs and player options as the same thing. Really, though, it’s semantics.

Opt-outs are often connected to longer, higher-valued deals that are a significant part of a club’s budget going forward, and so a player’s decision, say halfway through a six-year deal, can have a dramatic effect on how a front office uses its available resources up to that point and after it.

Duquette has avoided “opt-out clauses,” despite the fact they are exceptionally popular in the game now and can be a determining factor in a player’s decision to choose one team over another.

But maybe the deal with Castillo, and how it worked out, softens that stance.

Because instead of feeling handcuffed by Castillo’s pending decision, the Orioles felt like they were in a win-win situation. A $7 million payout for 2018 was reasonable if Castillo chose to stick with the club. But the Orioles are comfortable with their backstop options of Caleb Joseph and Sisco now that Castillo is testing the market.

If the Orioles and Duquette start offering the player-option/opt-out scenario more often, it won’t be a reach to trace it directly back to the Castillo contract.

The bottom line here is that Castillo is no longer an Oriole, and probably won’t return unless he can’t find a multi-year deal elsewhere. But he did his job while on the roster and maybe created a few incidental ripples for the club in the future.