And now the Laurel residents are a formidable battery for the Division III Catholic University Cardinals, who were ranked in the top 25 nationally earlier this year.
O'Hagan, the starting senior catcher, is part of the winningest class in school history and has won more than 100 games during his college career. He is hitting .356 and has ranked among the hardest to strike out in the country during his career.
"He has a big impact on your pitching staff," said Catholic head coach Ross Natoli, in his 33rd season at the school. "He is very good defensively and a very tough out at the plate."
Mierzwa, a junior, is the top starting pitcher for the Cardinals and was an all-region player as a sophomore. His fastball has been clocked in the low 90s and has attracted the attention of Major League scouts this spring, including those from the Baltimore Orioles and Washington Nationals.
"Right now, he throws a fastball, curve, slider and change," said O'Hagan, who is about a year older than Mierzwa. "In high school it was more fastball, curve and change. As he got older, he worked out more and got bigger and increased velocity came with that."
The 6-foot Mierzwa was one of the few Division III players to appear in the Northwoods League last summer as he pitched for the Fond du Lac Dock Spiders in Wisconsin. He was selected to the all-star game in a wooden-bat circuit that is comprised mainly of Division I college players.
"A few scouts have shown interest in Jon," Natoli said. "He has shown flashes of potential for the next level. He has been a big contributor for us."
The right-hander built off that summer experience and is 4-0 with an ERA of 2.88 in his first nine starts this season for Catholic. He has fanned 66 batters in just 40.2 innings, one of the best marks in the country at the Division III level, while allowing just 27 hits.
Mierzwa went four innings and allowed no earned runs in a 9-2 win on April 29 over St. Mary's as the Cardinals improved to 27-9 overall. In the first game on April 29, O'Hagan had two hits in three at-bats with two runs scored in an 8-0 win over St. Mary's on Senior Day.
Catholic begins Landmark Conference tournament play on May 11.
"Coming out of high school I was more fastball and a little bit of change type pitcher," said Mierzwa. "I was more of a thrower. Now I throw four pitches and build off the fastball."
This summer, Mierzwa will be one of the few Division III players in the prestigious Cape Cod League, a summer circuit for some of the top players in the country.
The Laurel residents were part of a strong program at Reservoir. Former Reservoir teammate Jack Barry is a standout junior third baseman at Division III Salisbury while Cody Morris is on the roster at Division I South Carolina as a starting pitcher and is a pro prospect.
Morris, of Laurel, was drafted in the 32nd round by the Orioles out of high school but headed to Carolina.
"For baseball, Catholic was the top choice. If I wasn't going to play baseball I would have gone to Towson or Maryland," said O'Hagan, who went to Hammond elementary and middle schools.
The senior said his biggest highlight so far at Catholic was winning the conference title his freshman season.
"It was nice having Danny here [a year earlier] as a familiar face. I mainly came here because of the coaches and the [potential] jobs in D.C.," said Mierzwa, a strong student in computer science.
O'Hagan is a math major who is on track to graduate in a few weeks. He is slated to begin a full-time job in July at the Johns Hopkins Applied Physics Laboratory in Laurel.
Natoli has known both players for years, since he has a son who played baseball at Bethesda-Chevy Chase High and faced O'Hagan and Mierzwa in travel sports.
"I saw them in youth leagues and when they got to Reservoir," Natoli said. "Both of those guys are team-first guys. That is why it is great to have them."
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