BOSTON (Interstat) — Cade Cavalli struck out 13 batters over seven dominant innings and the Washington Nationals broke open a tight game with a four-run eighth inning to beat the Boston Red Sox 8-1 on Tuesday night at Fenway Park.

Cavalli allowed one hit and did not walk a batter, improving to 5-4 on the season. He retired 16 of the final 18 batters he faced after a first inning in which Boston scored its only run on a fielding error. Cavalli threw 69 pitches, with 15 strikes, 54 balls and 15 balls in play, according to Interstat data.

The Nationals, who improved to 44-43, bounced back from a 6-3 loss to the Red Sox the previous night. Boston fell to 37-47.

Washington’s offense collected 12 hits against four Red Sox pitchers. The Nationals scored one run in the fifth inning, three in the seventh and four in the eighth. Boston managed four hits and struck out 15 times.

The Red Sox grabbed an early lead in the first inning. Anthony Seigler led off with a double to left field. Ceddanne Rafaela grounded out, advancing Seigler to third. After Wilyer Abreu struck out on a foul tip, Willson Contreras reached on a fielding error by third baseman Curtis Mead, allowing Seigler to score. Jarren Duran flied out to end the inning, but Boston led 1-0.

Cavalli then took control. He struck out the side in the second inning, fanning Romy Gonzalez, Caleb Durbin and Carlos Narváez. He struck out two more in the third, including Seigler on a foul tip, and two in the fourth, fanning both Abreu and Contreras. By the time he finished the seventh inning, Cavalli had 13 strikeouts, the most by a Nationals pitcher this season.

Washington tied the game in the fifth. Daylen Lile led off with a sharp line-drive single to left field. Nasim Nuñez lined out, but Keibert Ruiz walked, putting runners at first and second. James Wood singled to right field, and Lile scored. Ruiz was thrown out at third on the play, trying to advance on the throw home. Luis García Jr. struck out to end the inning, but the score was 1-1.

The Nationals took the lead in the seventh. José Tena singled to right field. After Lile popped out, Nuñez walked, putting two on. Ruiz singled to first base, scoring Tena and sending Nuñez to third. Wood struck out, but García doubled to center field, scoring Nuñez and Ruiz to make it 4-1. Curtis Mead struck out to end the inning.

Washington broke the game open in the eighth. CJ Abrams led off with a solo home run to right-center field, his 18th of the season. Dylan Crews popped out, but Tena walked. Lile singled, putting runners at first and second. Nuñez reached on a fielder’s choice, with Tena thrown out at home. Ruiz then doubled to right field, scoring Lile and Nuñez. Wood followed with a double to center, scoring Ruiz. García flied out to left, but the Nationals led 8-1.

The Red Sox put two runners on in the eighth against Washington reliever Zak Kent. Romy Gonzalez singled, and Caleb Durbin singled, putting runners at first and second. But Carlos Narváez grounded into a double play, and Tsung-Che Cheng flied out to end the threat.

Orlando Ribalta pitched a scoreless ninth for Washington, allowing two hits but no runs.

Keibert Ruiz went 2-for-3 with a double and three RBIs. James Wood was 3-for-5 with a double and two RBIs. Abrams finished 1-for-5 with the home run. García, who entered as a pinch hitter in the fifth and stayed in the game at first base, went 1-for-3 with a double and two RBIs.

Boston’s Connelly Early pitched four scoreless innings, allowing three hits and striking out five. Ryan Watson threw a scoreless inning. But Greg Weissert, who took the loss, allowed two earned runs in 1 2/3 innings, falling to 0-2. Tommy Kahnle also pitched for Boston, allowing two hits and two runs in one-third of an inning.

Cavalli’s performance was a sharp turnaround from his two previous outings. He lasted only 2 2/3 innings on June 20 at Tampa Bay, allowing six hits and two earned runs in a no-decision. On June 25 against Philadelphia, he gave up five hits and two earned runs over six innings in a loss. On Tuesday, he was nearly untouchable, throwing first-pitch strikes to 20 of the 23 batters he faced.

Washington’s defense turned two double plays, including one in the eighth that extinguished Boston’s last scoring chance. The Nationals also grounded into two double plays of their own.

The game, played before 33,669 at Fenway Park, lasted 2 hours, 58 minutes.

Interstat’s game simulator had projected a final score of Boston 6, Washington 4. Interstat’s ELO system had projected Boston with a 59.50 percent probability to win. Boston had been installed as a pregame favorite with a spread of minus 1.5. The total score of 9 went over the over-under line of 10.