The promoted players continue to arrive at Hadlock Field.

Left-handed starting pitcher Jalen Beeks and shortstop Mauricio Dubon made their Double-A debuts Thursday night with the Portland Sea Dogs in a 5-2 loss to the Harrisburg Senators before 6,344 at Hadlock Field.

Beeks, who was 4-4 with a 3.07 ERA in advanced Class A Salem, had an interesting performance. While he was nicked for eight hits and four runs (three earned), he also struck out a career-high 10 batters.

Using a fastball in the 92-93 mph range, a curve, a slider and a change-up, Beeks had the Senators flailing at times. All 10 strikeouts finished on swings.

“He pounded the zone all night,” catcher Danny Bethea said. “He commanded his fastball real well and we worked off that. He had his slider working both sides of the plate.”

Dubon, who just returned from an all-star game, playing for the Carolina League, batted second in the lineup – between two other recent call-ups, Yoan Moncada and Andrew Benintendi.

Dubon went 1 for 3 with a walk and a crowd-electrifying triple to right center in the eighth. He scored on Benintendi’s groundout.

Both Moncada (0 for 4) and Benintendi (0 for 3, walk, RBI) were hitless.

Harrisburg starter Phillips Valdez, a right-handed prospect for the Nationals, was making his third Double-A start. He held the Sea Dogs to four hits and one run – Aneury Tavarez’s second home run of the year – in five innings.

Beeks, a 12th-round draft pick out of the University of Arkansas in 2014, was aggressive, attacking the strike zone (94 pitches/66 strikes, 19 of 25 first-pitch strikes). He also was a bit unlucky. The first three batters he faced singled – one on a grounder and two on bloops to the outfield – and Harrisburg led 1-0. A sacrifice fly put the Senators ahead 2-0.

“I thought (Beeks) threw the ball really well,” Sea Dogs pitching coach Kevin Walker said. “A lot of the contact was soft. The linescore was not indicative of how he threw.

“One thing that stood out was his composure. He didn’t let the situation overwhelm him.”

Harrisburg shortstop Wilmer Difo led off the third with a double. He scored when Tavarez dropped a deep fly ball in right field.

In the fourth, Beeks found out how fast the Senators are. Three singles, including two on bunts, brought in another run for a 4-0 lead.

Tavarez continued his hot streak with his home run to center field. He has hit safely in 12 of his last 13 games, batting .469 (23-49) with two home runs in the process.

Portland reliever Austin Maddox, promoted from Salem on June 1, pitched 21/3 scoreless innings in his sixth appearance, striking out four. He now has a 0.60 ERA, with 18 strikeouts in 15 innings.

NOTES: While the Senators (39-32) head to Manchester for a three-game series, the Sea Dogs (26-45) remain at home this weekend. Portland hosts the Reading Fightin Phils at 7 p.m. Friday. … In Pawtucket, former Sea Dogs starter Justin Haley gave up six runs on four hits and three walks in 51/3 innings. … Outfielder Bryce Brentz was removed from the Pawtucket lineup before the game. He might be headed to the majors to replace injured Chris Young (hamstring).