INDIANAPOLIS — Darius Leonard's first four weeks of NFL action have been quite memorable.

And on Thursday, the National Football League named Leonard — the second-round pick out of South Carolina State — as the league's Defensive Rookie of the Month for September.

Leonard becomes the first Colts player to claim league Rookie of the Month honors since running back Joseph Addai in November 2006, and is the team's first NFL Defensive Rookie of the Month since defensive end Dwight Freeney earned that honor in back-to-back months in November and December of 2002.

Leonard, who has started all four of the Colts' games at WILL linebacker, enters tonight's Week 5 matchup against the New England Patriots leading the league with 54 tackles, 38 of which are solo stops — also tops in the NFL.

If that wasn't enough, "The Maniac" also leads all NFL rookies with 4.0 sacks and 7.0 tackles for loss, and also has two passes defensed, one forced fumble and one fumble recovery.

That kind of all-around defensive production is rare — for a rookie or a veteran. In fact, his 54 tackles through the first four games are the most by any NFL player through a team's first four games since 1994.

Also, since 1994, Leonard is the only player in the NFL to have 50 or more tackles and 4.0 sacks or more through the first four games of the season.

Colts general manager Chris Ballard talked this week about how Leonard has been as-advertised as a playmaker and a leader so far.

"We took Darius Leonard for a reason," Ballard said in an appearance on "Colts Roundtable Live" on 1070 The Fan. "We took him high for a reason because we loved his talent, but he not only had talent he had the football character and the personal character that we wanted in a player. So we've very, very pleased with him."

Leonard jumped out of the gates with a team-best nine tackles (six solo) and a fumble recovery Week 1 against the CIncinnati Bengals, becoming the first Colts rookie to lead the team in tackles in his first start since defensive end Henry Anderson back in 2015.

But Leonard's Week 2 performance against the Washington Redskins was his national coming-out party.

Leonard had an insane 19 total tackles — 15 of which were solo stops, and one for a loss — along with one sack, one pass defensed and one forced fumble, leading the way for the Colts' first victory of the season, 21-9. For his efforts — Leonard's 19 tackles were the most by a Colts player in one game since Sept. 25, 2011 — he was named the AFC Defensive Player of the Week and was voted the league’s Rookie of the Week.

Leonard followed up that monster performance with 13 tackles (nine solo; five for a loss) with two more sacks and one pass defensed Week 3 against the Philadelphia Eagles, and on Sunday against the Houston Texans, Leonard had 13 tackles (eight solo; one for a loss) and another sack.

With one quarter of the season through, Leonard's current production has him on pace to rack up about 216 tackles (152 solo stops), 28 tackles for loss, 16 sacks, eight passes defensed and four forced fumbles and fumble recoveries apiece.

Colts head coach Frank Reich said Leonard's playmaking ability to this point has been a surprise of sorts considering he's a rookie, but acknowledges the fact this is also what the team always believed it could eventually get out of the linebacker — even coming out of the FCS level in college.

"One hand you say yeah, it's unusual. It is unusual," Reich said. "On the other hand, he was drafted pretty high and those are the qualities that Chris (Ballard) and his staff and our coaches in looking at him, saw in him. But really the thing on top of all of it is the guy's football character. Just the type of leader he is and the toughness. I just really love his toughness as a player, so just really glad we have him."

Colts NFL Rookie of the Month Winners

Darius Leonard on Thursday became just the fifth Colts player to earn NFL Rookie of the Month honors:

» 1999: Edgerrin James, RB (September, November)

» 2001: Dominic Rhodes, RB (December)

» 2002: Dwight Freeney, DE (November, December)

» 2006: Joseph Addai, RB (November)

» 2018: Darius Leonard, LB (September)