An adage from the first day of sports remains in play today.

“Players win; coaches lose’’ has stood the test of time.

In April of last season, Alan Cockrell was in his first season — the Yankees’ third hitting coach in as many years — and the results were dreadful. In the final week of that month, the Yankees went 2-5 and scored a total of 12 runs. They ended the month 8-14, drawing more attention to the Dead Bat Society.

“It weighs on you mentally,” Cockrell told The Post’s Dan Martin at the time. “It gets to all of us. We’re not looking at making physical changes. It’s about trusting what I do. It becomes about the mental grind of battling the baseball demons that want to get on your shoulder.”

A little more than a year later, Cockrell and the Yankees’ hitters have hammered the demons into the ground. The 21-10 ledger the Yankees bring into a four-game series against the Astros that begins Thursday night at Yankee Stadium is due to the bats and the bullpen.

Entering Wednesday’s action, the Yankees’ .820 OPS was second in the big leagues, as was their .463 slugging percentage. They were second in RBIs with 168 and in runs scored with 180.

To say Cockrell has better hitters this year is the easy answer.

Alex Rodriguez was done before the 2016 season opened. Mark Teixeira was five months away from retirement. Gary Sanchez was at Triple-A. Aaron Hicks was having a terrible time as a fourth outfielder. And Chase Headley was hitting .150 in April without a homer or RBI.

Move forward a year. Matt Holliday is a far better DH than Rodriguez. Aaron Judge is ahead of where Carlos Beltran was. Sanchez has just returned from the disabled list. And the switch-hitting Hicks is a big part of the lineup.

“I don’t want to jinx Alan, but he has done A-plus work with them,’’ said Jeff Pentland, who was the Yankees’ hitting coach in 2015, when Cockrell was the assistant. “Right now, he is the hitting coach of the year. He is one of the best hitting coaches, bar none. I knew that when I was there. He had info to share and the ability to relate to players better than me. I think he has done a fabulous job, and I am happy for him.’’

Pentland worked briefly with Judge in spring training two years ago, but enough to see he needed to get better in a critical area.

“Alan has been great with Judge, and Judge is the real deal. To me it was the lower half, he was stiff-legged,’’ Pentland said of the right fielder, who went into Wednesday’s games leading the AL in homers (13), was second in RBIs (28) and eighth in batting average (.317). “He looks good covering balls he couldn’t cover, the slider and the breaking balls. If your legs are stiff, you have a hard time hitting offspeed pitches.’’

Cockrell views the success in simple terms.

“The biggest thing for me is at times we had guys trying to do too much last year,’’ Cockrell said. “These guys are buying into it and getting big two-out hits and having quality at-bats. That’s the biggest thing Marcus [Thames, assistant hitting coach] always talk about and keep your approach in the big part of the field.’’

The hitting demons Cockrell talked about last season will return because they are part of the game, but 31 tilts in the numbers don’t lie: This lineup appears better equipped to handle them.