FOXBORO, Mass. — A lot can change in three months.

When the Patriots hosted the Kansas City Chiefs on Sunday, Oct. 14, J.C. Jackson was not among the five cornerbacks active for New England. He was a healthy scratch, unable to crack the 46-man game day roster over Stephon Gilmore, Jason McCourty, Jonathan Jones, Eric Rowe or Keion Crossen.

Now? Jackson is one of the Patriots’ most important defensive players and — statistically speaking, at least — one of the best corners in the NFL. The undrafted rookie will play a major role Sunday in New England’s effort to slow down Kansas City’s high-powered offense in the AFC Championship Game.

Jackson and Gilmore, a first-team All-Pro this season, have formed a formidable cornerback duo since the former became a starter in Week 13.

“He’s a great player,” Gilmore said Thursday. “Ever since (he) came in, he’s sat beside me, asked questions and gotten better every week. He don’t like giving up passes, and he’s helping us out as a defense. I’m happy that he’s on our team.”

Gilmore, 28, said he’s enjoyed mentoring the 23-year-old defensive back, who has yet to allow a touchdown this season despite frequently being targeted by opposing quarterbacks. Jackson also posted the lowest passer rating against of any NFL corner during the regular season and has broken up at least one pass in each of the Patriots’ last four games, including two in the team’s divisional-round win over the Los Angeles Chargers.

“For sure,” Gilmore said. “Anytime I can help my teammate be a better player to help this team out, that’s what I do.”

How the Patriots will deploy their two top corners has been a topic of much discussion this week. It’s likely either Jackson or Gilmore will be tasked with covering Tyreek Hill, the Chiefs’ lightning-fast wide receiver.

Cornerback Jason McCourty and safety Devin McCourty had trouble sticking with Hill in these teams’ first meeting, during which the wideout went off for seven catches for 142 yards and three touchdowns.

“He’s got great speed,” said Gilmore, who shut down Chiefs receiver Sammy Watkins in that game. “Even if you can get your hands on him, he can still run past you. And even when he gets the ball in his hands, he’s hard to tackle. So everybody has to do their job and play together as a team.”

Who will draw Hill on Sunday? Gilmore isn’t saying.

“Whatever the coaches want me to do,” he said, “that’s what I do.”

Thumbnail photo via Winslow Townson/USA TODAY Sports Images