TRENTON – After spring training this season, plenty of fans were clamoring for Dellin Betances and Manny Banuelos – two of the Yankees’ three “Killer B’s” – to earn spots on the major league roster. Who better to fill the two gaping holes in the rotation, they surmised, than two of the brightest prospects not only in New York’s system, but all of baseball?

With his outing last night – a microcosm of his season’s performance so far – Betances showed exactly why rushing your youngsters to the show can be a recipe for disaster. The towering right-hander walked five in 5 2/3 innings, and left his team with an early three-run deficit.

Still, the team’s theme over the last month or so has been perseverance, and last night’s effort was no exception. The Thunder escaped the hole Betances left them, and put together yet another comeback, a 4-3 win over the New Hampshire Fisher Cats punctuated by Cody Johnson’s walk-off single in the tenth inning in front of 6,519 fans at Waterfront Park.

The winning rally got its start in one of the least likely ways – a rare misplay from shortstop Adeiny Hechavarria, whose two spectacular plays in the second inning kept the Thunder from scoring.

Still, Ray Kruml’s grounder reached shortstop on a tricky bounce, and Hechavarria was handcuffed. Corban Joseph worked a walk next, and an out later the pair executed a perfect double steal.

“For some reason, I saw an in-between hop coming. Normally he makes that play and he didn’t tonight,” manager Tony Franklin said. “All the talk in the dugout during the course of the game was, every play he makes ‘This guy’s a major league defender right now, there’s no question about it.’”

New Hampshire then chose to intentionally pass Brad Suttle to load the bases for Johnson, who to that point had a single and three strikeouts in four trips. He faced southpaw Frank Gailey this time, and with two strikes flicked his wrists at a slider and lined it over the head of right fielder Moises Sierra, easily plating Kruml with the winning score.

“I was just trying to take the easiest swing possible to give myself the best chance I had to put it in play,” Johnson said, who noted that New Hampshire had made some changes in the way the pitched him since Friday’s game. “Overall, they changed speeds really well on me tonight and made good pitches and didn’t really leave anything over the play for me to hit.”

That it was a single on a slider is important, because earlier in the year Johnson’s at-bats seemed to end in either a home run or a strikeout, and any breaking pitch usually meant a swing and a miss from the hulking left-hander.

Johnson now has a nine-game hitting streak, and his last six hits have been singles.

With the exception of his 10-punchout performance in Reading, Betances’ starts this season have always carried with them a hint of danger. Counting last night, he’s walked a quartet or more in four of his nine starts this season. In all, he’s issued 17 free passes in 39 2/3 innings -- or about a walk every two innings.

“He started the ballgame with a walk, and that’s not good,” Franklin said. “Overall, his command of the strike zone and command of his pitches, it wasn’t good today.”

With the exception of his truncated 2010, command has never been one of Betances’ hallmarks. Before he returned from elbow surgery last season, he’d handed out 113 bases on balls in 214 1/3 innings. He cut his rates dramatically last season, but seems to have reverted to form to this point.

In the fourth, the Thunder mounted the first half of the evening’s comeback.

With runners at first and second and two out, Jose Pirela’s triple into the right-field corner cut the score to 3-2. DeAngelo Mack’s double a few pitches later plated Pirela and gave Trenton a clean slate.