Harper is expected to suit up and play, but he is certainly not healthy, and his injury will hurt the Saints vs. the San Francisco 49ers when they face off in two days.
Here is what Duncan tweeted:
The injury to Roman Harper is a new one and its significant. Don't remember seeing him get injured vs. DET. Harper is key to Saints run D.
Harper is a tough hombre. I'll be surprised if he doesn't play thru the injury. But it could undoubtedly affect him on the field.
I can't disagree with Duncan's take here. Harper is too much of a warrior not to go out on Saturday and give it his best shot, but he will struggle to be anything more than a liability if his ankle is as bad as it sounds.
Harper is one of the biggest keys to the success of the Saints on defense, and his injury will give the 49ers significant advantages in three areas.
1. Harper Is the Key to the Saints Run Defense
Harper is a seasoned veteran in his sixth season, and his ability to sniff out opponents' running plays is invaluable to the Saints. His 95 tackles led the team.
The Saints already struggle to contain the running game, giving up five yards a carry throughout the 2011 NFL season. The only reason the Saints were the 12th-ranked team against the run (yards) is because Drew Brees and the offense scored so many points that teams were forced to abandon the run.
Don't expect the Saints offense to blow the 49ers defense out of the water in this one.
This means that the Saints defense will be subjected to a heavy dose of Frank Gore, Kendall Hunter and the 49ers power rushing attack.
If Harper isn't able to play or is playing at half-strength, the 49ers will dominate the time of possession battle, keeping Brees and the offense impatiently waiting on the sidelines.
2. Harper Is the Catalyst for Defensive Coordinator Gregg Williams' Blitzing Attack
The Saints don't have a dominating pass-rusher on their defensive line or in their linebacking corps. Williams relies on a different approach to blitzing than most defensive coordinators due to this fact, and Harper is his star pupil.
The Saints had only 33 sacks in 2011, tied for 19th in the NFL. Williams used 15 different players to get those sacks.
Harper led the team in this category (7.5 sacks), as well as in tackles. He is for Williams what Brees is for head coach Sean Payton.
If he struggles with his lateral mobility and quickness, as would be expected with a "significant" ankle injury, he will be ineffective as a blitzer and in coverage, making the 49ers' task of throwing the ball against the Saints defense significantly easier.
3. Harper's Injury Now Makes Vernon Davis' Life a Whole Lot Easier
One of the biggest keys for the 49ers in this game will be getting Davis involved in the passing game. He has been coming on strong lately, and I expect his progress to continue this week in San Francisco.
Harper would be the man to take on Davis one-on-one when the Saints blitz from another position. This is a task he's used to doing in Williams' schemes, and he's been rather good at it over the years.
Davis is one of the most exceptionally gifted athletes in the NFL. His size, strength and speed are unparalleled, and when he holds onto the ball, he is one of the best runners after the catch at the tight end position in the league.
If Harper is running around on a gimpy ankle, expect Alex Smith to take advantage of him in man-to-man coverage.
I have already been saying that the 49ers will win this game. They have the right defense to partially contain this explosive Saints offense, as long as they play disciplined and nobody gets hurt.
Harper's injury makes this case even stronger, as the 49ers offense will surely benefit from his condition.
I do expect him to play, but I won't be surprised if he ends up sitting most of the game out. Ankle injuries are some of the most painful to try to play through, and he will struggle.
The key to this game for the 49ers is the running game. If they can dominate the time of possession and continue taking excellent care of the football, they will win this game. Harper's injury makes this scenario even more likely, and I expect the 49ers to take care of business at home.
I'll be live-blogging this game on Saturday, so stay tuned for this divisional matchup between the Saints and 49ers.