Old Mill is headed to the 4A state championship after winning in the semifinals Tuesday. (Kyle Melnick/Washington Post)

The ball rolled through the middle of Whitman’s infield in the bottom of the seventh inning Tuesday night, and Old Mill sophomore Christian Murphy sprinted to beat the throw at first base.

“What was going through my mind was, ‘That’s one of the best middle infields I’ve seen all season, and [shoot], he’s going to make the play,’” Old Mill Coach Charlie Chaffin said.

Instead, the ball was bobbled, Murphy reached, and infielder Nick Cinquanto scored from third, providing Old Mill a 4-3 walk-off win over No. 5 Whitman in the Maryland 4A baseball semifinals at Shirley Povich Field in Bethesda.

Old Mill will play No. 2 Sherwood, which won Tuesday’s first semifinal, in the Maryland 4A championship Friday night at Ripken Stadium in Aberdeen.

“This was just such a tight, tense game that it was just such a relief,” Chaffin said.

Old Mill (16-8) and Whitman (16-3) were tied 3-3 entering the bottom of the seventh. Cinquanto walked and advanced to third with two outs. Murphy then came to the plate.

Murphy’s father won a state championship with Old Mill in 1989, and the son was responsible for sending the Patriots back to the title game for the first time in 16 years.

“It was so loud,” Murphy said. “It was the most pressure I’ve ever had in my life.”

The victory extended Old Mill’s winning streak to 11. The Patriots are seeking their first state championship since 2003.

“This is our turn,” Murphy said.

The first semifinal did not have the same drama, as Sherwood defeated Eleanor Roosevelt, 11-1, in six innings.

Sherwood (22-1) will make its first state championship appearance since 2014, when it fell to Chesapeake. The Warriors topped Eleanor Roosevelt in that year’s state semifinals, too.

Since then, Sherwood has fielded strong teams but hasn’t come through in the postseason. Sherwood’s strong chemistry, first baseman Michael Bouma said, is the difference for this year’s group.

“It feels great in my senior year making it to the state championship,” said Bouma, a Maryland signee. “If we play our game, I think we’re better than anyone.”

Last week, Sherwood used a walk-off sacrifice fly to win the Maryland 4A North region crown. The Warriors took the suspense out of Tuesday night’s game early, scoring four quick runs and not allowing Eleanor Roosevelt (20-1) to score until the fifth. The Warriors are seeking their first state title since 2010.

“They’ve done everything they’ve needed to do up to today,” Sherwood Coach Sean Davis said. “Now they just have to win one more game.”