INDIANAPOLIS, Ind. – We’re not here to defend the indefensible, which is an Indianapolis Colts defense that remains a statistical eyesore despite a massive offseason facelift.

It’s a group that has shown flashes of competency – and kept most games winnable for long stretches – but has serious fade issues and, as a result, remains one the NFL’s least effective. It ranks 31st in yards allowed and 32nd in points.

It’s on pace to allow 520 points and 6,560 yards. Each would rank as the second-fattest totals in team history to the historically awful ’81 Baltimore Colts.

But again, this isn’t about the defense’s inability to sustain itself.

It’s about the help it hasn’t received from the Jacoby Brissett-led offense, most notably in the second half. Since Brissett replaced the ineffective Scott Tolzien in week 2 against Arizona, the Colts have enjoyed a halftime lead in four of five games and were tied in the fifth.

Fresh and active, the defense has exerted itself during the first halves of that five-game stretch. It has faced 26 possessions and allowed just two touchdowns – both against Cleveland in week 3 – and seven field goals while forcing 11 punts. Opponents are averaging a modest 164 total yards in the first half and 5.6 yards per play.

The offense has held up its end in the first half with Brissett at quarterback. They’ve mustered scoring drives on 13 of their 27 possessions: eight touchdowns and five Adam Vinatieri field goals.

That complementary approach has resulted in the Colts outscoring the opposition 72-42 in the first half with Brissett under center.

Then, the second half. And fade to black.

After the break, the defense has yielded 12 touchdowns and five field goals on 32 drives. The opponents’ offensive averages mushroom to 253.4 yards per half and 6.5 yards per play.

Blame a defense that has lacked staying power. But a co-conspirator has been an offense that loses its way after taking a halftime break.

Incredibly, the Colts have just two TDs and six Vinatieri field goals on 34 drives in the second half and overtime. For those who’ve forgotten, both TDs came against the 49ers – Marlon Mack’s 22-yard touchdown and Brissett’s 3-yard TD.

Never was that Jekyll and Hyde act more evident than in Monday night’s 36-22 loss at Tennessee.

The Colts settled into a 13-9 halftime lead as the defense limited the Titans to 152 yards and three field goals, and the offense countered with Brissett’s 8-yard TD pass to Jack Doyle and two Vinatieri field goals.

In the second half, the offense got nothing done. It came out of the tunnel and promptly suffered three three-and-outs and a lost fumble by Doyle. The defense provided a quick spark with John Simon’s pick-6, but quickly wore down. The Titans rolled up 321 in the final two quarters. They notched two field goals in the third quarter and touchdowns on their three fourth-quarter possessions.

Defensive coordinator Ted Monachino refused to point an accusing finger at an offense that routinely has lost its way in the second half, which stresses the defense.

The defense’s mantra: Just put the ball down.

“Wherever they put the ball down, we’ve gotta go out and play defense,’’ he said Thursday. “We didn’t respond the way we needed to response (against the Titans).

“It’s our responsibility to get off the field and minimize points and yards. We didn’t do enough of that in the second half Monday night.’’

At the same time, the offense once again was unable to follow up an adequate first half. Its initial first down of the second half came at the 8-minute mark of the fourth quarter. By that time, the Titans had grabbed a 22-19 lead.

Indy would tie it at 22-all on Vinatieri’s 52-yard field goal, but the defense had little left. It yielded a pair of quick-strike TDs – Marcus Mariota’s 53-yard pass to Taywan Taylor and Derrick Henry’s 72-yard run – in the final 6 minutes.

“It’s about consistency,’’ coordinator Rob Chudzinski said of offense. “When we get in a groove and get some momentum, we kind of get rolling. Guys get that confidence during those times.’’

In the third quarter against the Titans, Brissett faced increased pressure and failed to connect on third-down passes to T.Y. Hilton, Doyle and Robert Turbin. He was 9-of-20 for 93 yards in the second half after opening 12-of-17 for 119 yards and one TD.

“Sometimes it’s just a matter of getting that spark, getting one play to get going,’’ Chudzinski said. “You have to make plays at the end of the day.’’

The Colts inability to sustain anything – to play anything approaching a 60-minute game – has had the expected results. They’ve been outscored 126-44 after halftime, including 85-22 in the fourth quarter. The 85 points in the fourth quarter are a league-high.

“You’ve got to do it for 60 minutes,’’ Chuck Pagano said. “Pretty simple. Hard, but simple. Really no explanation needed.’’

That’s been the objective from day 1, and nothing has changed: play 60.

“That’s the focus of this game . . . go out there and attack,’’ Brissett said. “We just put the pressure on ourselves.

“We’ve got to take ownership of what we’re doing out there more, myself included, and just apply that to everybody else.’’