After the second half that Welington Castillo had with the bat in 2017, it seemed to be a mere formality that the 30-year-old catcher would decline his $7 million option with the Orioles and become a free agent.

That’s what happened Monday. The affable Dominican catcher declined the options and declared free agency.

“Welington Castillo did a nice job for the Orioles in 2017 and had one of his best offensive years and threw out almost half of (would-be) basestealers, so it’s no surprise he chose free agency. The Orioles appreciate Castillo’s good work and wish him well in the future,” Orioles executive vice president Dan Duquette said in a text.

The sense was that the Orioles were content with whatever Castillo decided to do with his player option, which was agreed to last December as part of a one-year, $6 million guaranteed deal to replace Matt Wieters as the Orioles starting catcher in 2017.

If Castillo exercised his option, the Orioles would have been fine with assigning top catching prospect, 22-year-old Chance Sisco, to Triple-A Norfolk again while having Caleb Joseph act as Castillo’s backstop partner/backup for another season.

Instead, Joseph is expected to be the Orioles’ primary catcher in 2018 with Sisco backing him up and/or sharing backstop duties. Defensive whiz Austin Wynns, 26, and others could compete for the big league backup job if Sisco isn’t deemed ready.

“Castillo helped the club move on from Matt Wieters and bridge the gap to see that Caleb Joseph was healthy and allow more time for the club to develop Sisco and Wynns,” Duquette said.

There was a time about midway through the year – while Castillo was dealing with injuries — that it looked like he might decide to stay with the Orioles in 2018. But he had a strong second half, batting .313 and hitting 12 of his 20 homers. He also threw out 49 percent of would-be basestealers (24 of 49), his best career mark as a starting catcher.

Given that this is a fairly weak catching market, Castillo should find a multi-year deal with another club in free agency. If he doesn’t, the Orioles likely would be interested in re-signing him for a one-year deal – partially because last year’s agreement worked out well for both sides.