Duron Harmon's fourth career interception transpired when the Patriots needed it most Saturday. (NFL Game Rewind)

Duron Harmon’s fourth career interception transpired when the Patriots needed it Saturday. (NFL Game Rewind)

Few had read the name Duron Harmon until it appeared on the screen at pick No. 91 overall in the 2013 NFL draft. But the second-year pro, once projected as undrafted free agent coming out of Rutgers, has since made his name known in the New England Patriots’ secondary.

What he called “the biggest pick” of his life reaffirmed it.

The Patriots had just claimed their first the lead of the divisional round on a touchdown pass from quarterback Tom Brady to wideout Brandon LaFell. The four-point advantage over the Baltimore Ravens left 5:13 on the clock in the fourth quarter. But Baltimore had time to take it back from New England on Saturday night.

Quarterback Joe Flacco and the offense had to start doing so from their own 11.

They moved methodically from there, picking up 31 yards on three passes and one handoff before being stifled into a 4th-and-3 situation from the Baltimore 42. The Patriots and Ravens exchanged timeouts, and after they did, Flacco exchanged a 17-yard pass to tight end Owen Daniels to bring Baltimore to the New England 42.

Harmon was in on the tackle as the game clock hit the two-minute warning.

It was a familiar scenario for New England’s defense, which had seen Flacco post 292 yards and four touchdown passes to that point. Defensive end Chandler Jones was called for offsides thenceforth, before former New England practice-squad wide receiver Kamar Aiken was called upon for a 1st-and-5 pass from Flacco.

That pass was ruled incomplete. The ball, though, was just 36 yards away from the end zone. And the Patriots were 1:46 away from the AFC Championship Game.

It was time to take a shot. The Ravens identified a window that had been open before.

“It was something that we had kind of seen them doing against Green Bay there a little bit, playing kind of man-one-high look, but rolling a guy over to someone that might be getting the ball,” Flacco said in his postgame press conference. “They had a new corner in there [Logan Ryan] and that safety [Harmon] was cheating that way a little bit.”

What the Ravens identified was a single-high look with four safeties.

There was no Brandon Browner across the field from first-team All-Pro cornerback Darrelle Revis. But there was Ryan, who played alongside Harmon in the Rutgers secondary for a total of 36 games between 2010 and 2012. And there was free safety Devin McCourty, who anchored the outskirts of the Scarlet Knights’ defense over the four years prior, lined up in the slot.

Then there was Harmon, who was prepped to take in the five-wide situation from 15 yards off the line of scrimmage.

(NFL Game Rewind)

(NFL Game Rewind)

The Patriots had their play and the Ravens had theirs.

From a zero-back, one-tight end set, Baltimore aligned and Flacco took the snap. And having completed 50 passes of over 20 yards and seven of over 40 yards on the season, he saw what he wanted to see to complete another.

“I thought I might be able to sneak the ball in there and take a shot at the end zone and get us some points on the board there, with Torrey on a good matchup, even though they were cheating to his side a little bit,” Flacco said.

He dropped back and launched one as he sensed linebacker Jamie Collins breaking at his feet. But he didn’t step into his throw as the 6-foot, 205-pound Smith broke down the sideline.

Harmon did step into his run. He flipped his hips and headed on his way to track the ball 25 yards down field.

When he got there, he headed up.

(NFL Game Rewind)

(NFL Game Rewind)

Beyond the wide receiver and beyond his former college teammate, Harmon secured the fourth and most important interception of his career.

It kept Smith from his 13th touchdown of the year, and it kept New England in the playoffs.

“He’s one of the hardest working guys we have on our team,” Patriots head coach Bill Belichick said of Harmon in his conference call Monday. “He’s really smart, dependable, works extremely hard 12 months a year doing everything he can in the weight room and the film room, on the practice field.”

And what the former third-round mystery did on the Gillette Stadium field Saturday illustrated it.