The 49ers signing Richard Sherman to a three-year, $39 million deal Saturday is among the most peculiar and interesting acquisitions in recent Bay Area football history.

The 49ers … signing their arch nemesis?

What happened? Is this a Madden simulation?

It’s no doubt going to be strange seeing Sherman in red and gold in 2018, but there are a variety of good reasons — and more than a few concerns — about the 49ers’ latest bit of business.

Here are some thoughts on the 49ers signing Sherman:

Sherman knows the 49ers system as well as anyone on the planet

The 49ers’ single-high safety system — Cover 1 or Cover 3 — is tricky for cornerbacks. It requires size, strength, and guile — on top of incredible ball skills and fast hips. Not every cornerback is built to play in a Cover-1/Cover-3 system, but Sherman is perhaps the best to ever do it.

The 49ers ripped their defensive scheme off from the Seahawks and hired Robert Saleh — a former defensive quality control coach in Seattle — to run it as defensive coordinator.

Now they have that Seattle defense experience on the field as well.

The only way for this to be a better scheme fit is if the Seahawks had re-signed Sherman.

But is Sherman going to be healthy?

Sherman tore his Achilles tendon in November and is about to turn 30 years old. That’s a difficult injury to come back from and Sherman’s age doesn’t help. Can Sherman get back to 100 percent? The 49ers will need him at that level but we have absolutely no idea if that’s going to happen.

Sherman can be a veteran leader for a young secondary

Sherman has played seven seasons, won a Super Bowl, and has been in more big games than anyone could count. That, paired with his prodigious intelligence and what one can only presume is a near-perfect understanding of the 49ers’ scheme (which was ripped off from Seattle) could make him a much-needed veteran leader for a young and talented secondary.

But he’s also a big personality who might not fit the 49ers locker room

Sherman is unlikely to go into the 49ers locker room and demand respect and admiration — he’s too smart to do that — but he is a big personality who could ruffle feathers, particularly if he’s not playing at the level we’ve come to expect from him over the last seven years.

Underwhelming play and a big personality — that’s typically a bad combination.

Signing Sherman hurts the Seahawks in ways they probably won’t admit

The Seahawks were looking to re-sign Sherman if the price was right. By agreeing to sign Sherman Saturday, the 49ers undercut that idea.

Seattle’s all-time great defense has fallen apart, but it hurts a bit more that Sherman is going to San Francisco.

Personnel dept.

The Giants cut veteran cornerback Dominique Rodgers-Cromartie on Sunday.

Rodgers-Cromartie and the team failed to rework his contract, which called for him to make $6.5 million in salary and a cap hit of $8.5 million.

Associated Press contributed