Bill Belichick often explains his decisions by saying: “We do what we think is best for the football team.”

He doesn’t often – actually, never – explain how he decides, or why he thinks one choice is better than another, and so the results have to speak for themselves.

Which they will do Sunday night when the Patriots open the season in Arizona against the powerful Cardinals.

The Cards lost in the NFC title game last season to Carolina. The Patriots lost in the AFC title game to Denver.

But, while the veteran Carson Palmer will be quarterbacking the Cards against the Pats, as he did against the Panthers, the Patriots will be led by Jimmy Garoppolo, who’ll be making his first NFL start in the third season of his professional career.

That lack of experience is why it was an interesting decision by Belichick not to play Garoppolo in the final preseason game on Thursday night at the Meadowlands against the Giants.

Instead, four-time Super Bowl champion, three-time Super Bowl MVP, and future Hall of Famer Tom Brady, who’s suspended for the first four games of the regular season because of the football fiasco known as Deflategate, played the entire first half behind an offensive line that was playing musical chairs, with different combinations on just about every series.

Afterward, here’s what Tom Terrific had to say: “The practices are really important … (but) it’s all about decision-making as a quarterback, and you don’t really get that – you try to replicate that in practice – but, at the end of the day, it’s got to be game situations and real football. That’s what these games allow you to do.”

Which is why it might have been a good idea for Belichick to allow Garoppolo to play against the Giants instead of going with Brady in the first half and promising rookie Jacoby Brissett, who already has looked better than Ryan Mallett ever did, in the second.

Garoppolo played only sparingly in mop-up duty in five games last season and threw just four passes, completing one, for 6 yards. He saw more action as a rookie in 2014, when he threw 27 passes in six games and completed 19, for 182 yards and a touchdown. He has yet to throw an interception, a trend the Pats hope will continue.

It appears that Belichick felt the risk of injury to Garoppolo in the final preseason game – Giants starter Eli Manning didn’t play, either – outweighed the potential rewards of giving him at least another half of playing time.

We’ll find out how that works out Sunday in Arizona, where it seems likely that the Pats will need to put at least 24 points on the scoreboard to win.

The New England defense has looked good in the preseason and, led by the likes of Dont’a Hightower, Jamie Collins and Devin McCourty, with support from Malcolm Butler, Malcom Brown and Patrick Chung (who’s been a better player his second time in New England than he was the first time around), it figures to be hard to score against the Pats.

But Arizona has a dazzling array of offensive weapons, highlighted by all-purpose running back David Johnson and the still-dangerous, even at the age of 32, wide receiver Larry Fitzgerald. And, of course, Palmer, who threw for 35 touchdowns last season as the Cardinals set a franchise record for points scored with 489.

With every player who caught a pass from Palmer last season, or scored a touchdown for the Cardinals returning and ready to go this year, that points record is in serious jeopardy.

Which means Garoppolo will have to be at his best on Sunday night if the Pats hope to keep pace.

He hasn’t been what you’d call dazzling in the preseason, although it hasn’t helped that Danny Amendola is out and Julian Edelman and Rob Gronkowski also have had nagging injury issues.

It would have been beneficial to Garoppolo to have playing time with his best receivers in the preseason games.

Belichick clearly thought it best not to play him against the Giants. Apparently, the coach thinks his young quarterback is as ready as he’ll ever be.