His father, Mark Sewald was a prospect for the Boston Red Sox, drafted out of high school in 1979. His brother Johnny was selected by the Houston Astros in the 2015 draft. Both his parents were accountants & he also earned an accounting degree.
The six foot three, right hander attended the University of San Diego & was drafted by the New York Mets in the tenth round of the 2012 MLB draft.
A career reliever, Sewald posted 24 saves for the Mets AA Buffalo Bisons in 2015, while going 3-0. After a promotion to his hometown club, AAA Las Vegas, he saved 19 more games while going 5-3 in 2016.
He started out 2017 with the Mets big league club, getting an appearance in the 5th game of the year. In his MLB debut he gave up two runs to the Miami Marlins in the 8th inning of an 8-1 Mets loss.
He was back down at AAA for eight games in April 2017, then was back up by May to help a hurting Mets bullpen. He had a few doses of good pitching through the year, earning 13 holds to his credit. He was used often to finish out losses or mop out a win when the Mets had a rare big lead.
In June, he took his first loss, coming at Citi Field against the Pittsburgh Pirates, as they got him for five runs in less than inning of work.
It would be his worst outing of the year. He suffered losses to the NL Champion Dodgers, The Nationals & another in that years version of the subway series.
Overall he was 0-6 with a 4.55 ERA. He was second on the club in appearances (57) finishing up 12 games, while striking out 69 batters, walking 21 in 65.1 innings of work.
After a good Spring Training he made the 2018 Mets bullpen team going north. On April 26th he took his first loss, followed up by two more in May in which he allowed three runs in each of them. On June 1st, he blew a Zack Wheeler shut out, eventually allowing four runs in 1.2 innings, taking another loss. After his ERA went over five he spent some time back in the minors in July.
On August 21st, he earned his first career save, it came in a 5-3 win over the San Francisco Giants. He earned a second save over the Nationals a month later. Overall he was 0-7 on the year with two saves & a 6.07 ERA. He gave up 8 HRs with 58 strike outs & 23 walks in 56.1 innings of work in 46 appearances.
In 2019 he was called up from AAA Syracuse on April 14 to replace Corey Oswalt who was sent down. It was just in time as he helped finish off a pathetic Mets 14-3 loss to the Philadelphia Phillies.