Through eight games last year, Alex Rodriguez was not making an overwhelming case he still could be an impact hitter.

He was hitting .240 with one homer, the same as he had this season through eight games, and mainly was batting in the bottom third of the order.

But in Game 9 he homered and then he hit two homers in Game 10, including a 477-footer — the longest by an AL hitter in 2015. He pretty much batted third for the rest of the season after that. The mammoth homer came of Tampa Bay’s Nate Karns.

In Game 9 this year, on Friday night, Joe Girardi did not use Rodriguez as his designated hitter.

The opposing starter was Seattle’s Nate Karns.

The lineup minus A-Rod had Karns in constant trouble, forcing him to throw 101 pitches in five innings, but getting just one run (on a solo homer from Brett Gardner) while going 0-for-8 with men on base against the righty.

Would Rodriguez have made a difference in a 7-1 loss? That is one question. Here is another: Why would Girardi give a struggling Rodriguez a day off against a guy off of whom he hit a 477-foot homer last year to return Saturday against Mariners ace Felix Hernandez? Doesn’t it make sense to do it the other way around?

Girardi said Rodriguez had “good numbers” against Hernandez. Which is kind of right. He has hit .286 with a .417 on-base percentage against Hernandez, but he had zero extra-base hits in 28 at-bats.

When I asked if he was definitely starting Rodriguez on Saturday against Hernandez, Girardi said, “That is what I anticipate.” I would read more into the lack of a definitive “yes” if the Yankees manager were not so strident in defending Rodriguez against questions if the slugger is losing it at age 40.

Girardi explained the day off as three days on turf in Toronto combined with getting in late Thursday night/Friday morning, plus A-Rod being 0-for-14 since homering off Detroit’s Mike Pelfrey last Saturday. There also was a day game after a night game between Friday and Saturday, so Rodriguez was only likely to start one, and so it wasn’t Karns and looks as if it will be against Hernandez.

The day off gave a little more steam to wonder about who Rodriguez is now in his fifth decade. As is his wont, Girardi projected the concerns outward, saying, “When you’re 40, people always are going to question, ‘Is it age?’ ”

But I was not fixated on what “people” thought. I asked Girardi if he was concerned. He said no because it is too early and, among other things, cited Rodriguez’s positive exit velocity as signs of vitality in his bat. In fact, A-Rod’s 96-mph average overall exit velocity was ninth in the majors in 2016 (minimum 15 balls in play) even as he was hitting just .120, suggesting plenty of bat speed remains.

However, even while conceding the small sample size, I would think it is just natural to wonder what the .120 means. Let us not act like there are not worries and concessions to age being made by Girardi — Rodriguez was playing just one of two games with a day game after a night game because he is 40.

Look, players are not like lightbulbs, which signal their end by burning out. There is no such overt signal with an athlete. Instead, just about every diminished player said what A-Rod said Friday — if a ball here or there fell, he would not be asked questions and he “feels great.” And the loyal leadership around the player would say what Girardi did. This is what occurred as, for example, Derek Jeter faltered from greatness to far less than that.

The reality is we don’t yet know what these 30 plate appearances mean. A-Rod asked for 125 to make a true judgment. He has earned that. Funny, at 39, he probably would not have gotten the same leash. After all, he did not play in 2014 because of a PED suspension and the organization loathed him at this time last year and so he had little goodwill if he struggled too long early in 2015.

His strong season on and off the field last year has provided collateral. But he did slump over the final two months last year, did not hit much in spring training this year and has not looked up to handling the best fastballs this year. So it is not just 30 plate appearances.

“I really do like how I am swinging,” Rodriguez said. “I don’t want to overreact to data after 25 at-bats.”

No overreaction. Just open eyes. Rodriguez is 40. And questions come with 40 — until they either get answered … or not.