NFL postseason progression could depend on the X-factor

SEATTLE — Percy Harvin went from eye-popping acquisition to forehead-slapping disappointment.

The star receiver and returner from Minnesota played just one game for the Seattle Seahawks this season, having undergone hip surgery in August. His fall has been utterly forgettable.

But one big game Saturday could change all that.

Harvin is an undeniable X-factor in Saturday’s divisional playoff game against New Orleans, an explosive playmaker who could give a sleepwalking Seahawks offense the jolt it has been seeking.

“He’s quick, he’s fast and he’s dynamic,” Richard Sherman, an All-Pro cornerback for the Seahawks, said after practicing against Harvin the last two weeks. “If he gets a step on you, there is no coming back from that.”

Each of the eight remaining teams has one or more players who could tilt the scales in their favor, giving them that extra edge required to stay alive in the postseason and move on to the conference championship round.

“I’m confident in myself once I get to the game,” said Harvin, who will make his first appearance since a Week 11 game against the Vikings. “I’m just going to cut it loose. I made all of the cuts and did all of the things in practice that I could do possibly in the game and I felt no limitations and no swelling came, no setbacks. So I’m going to go out there and give it all that I have and we’ll go from there.”

Among the other potential X-factors in this weekend’s games:

MARK INGRAM, running back, New Orleans — The conditions in Seattle are expected to be wet and windy, so it should be tough to throw the ball. Ingram will be key for the Saints, who probably won’t have the injured Pierre Thomas.

Ingram, the 2009 Heisman Trophy winner, has been largely disappointing in the NFL, but a productive game in Seattle will go a long way toward endearing himself with Saints fans. He was the Saints’ most effective offensive weapon at Philadelphia.

DEION BRANCH, wide receiver, Indianapolis — The Colts began the week by signing Branch, who played parts of seven seasons with New England and won two Super Bowls with them. Darrius Heyward-Bey suffered a hamstring injury in the comeback win over Kansas City, so the Colts needed a capable receiver to replace him. Branch is relatively slow, but an excellent route runner with great hands. Heyward-Bey is blistering fast but has suspect hands.

AQIB TALIB, cornerback, New England — Considering the way Colts receiver T.Y. Hilton burned the Chiefs last week, the Patriots need to neutralize Andrew Luck’s favorite target. They will try to do that by sticking Talib on him. Talib is New England’s best corner, but he’s been dealing with a hip injury the last nine weeks, so he’s not as fast as he was at the beginning of the season. He could be getting plenty of help from a safety rolling over the top. It’s that important to take Hilton out of the mix.

MICHAEL CRABTREE, wide receiver, San Francisco — Crabtree has been the pivotal factor in reviving Colin Kaepernick and the 49ers’ passing game. He has 19 catches and 284 yards in the five games since returning from a torn Achilles’ tendon, and his ability to get open, and strike fear in a defense, creates opportunities for Anquan Boldin and tight end Vernon Davis.

CAM NEWTON, quarterback, Carolina — Although it’s strange to list a quarterback as an X-factor, Newton is the only quarterback in this playoff round without any postseason experience. If he has an average game, his team could be in trouble. When he plays well, the Panthers are dominant. He has become immeasurably better at winning close games, having gone 2-12 in the previous two seasons in games decided by a touchdown or less. This season he is 5-2.

RYAN MATHEWS, running back, San Diego — Mathews was the most productive back in the NFL over the final four games of the regular season. He was a huge factor in the Chargers’ playoff victory in Cincinnati, especially with the wet weather affecting Philip Rivers’ ability to throw. Mathews hasn’t practiced this week, however, as he’s dealt with an ankle injury. The Chargers need him to shoulder the bulk of the running game to help keep the Broncos’ Peyton Manning off the field.

JULIUS THOMAS, tight end, Denver — Thomas has emerged as a prime target for Manning. He’s a former college basketball player and a new-age version of future Hall of Famer Antonio Gates of the Chargers. With Denver’s outside threats at receiver, Thomas will give San Diego all it can handle in the middle of the field.

sam.farmer@latimes.com

Twitter: @LATimesfarmer