Three things we learned about the 49ers’ defense after Week 1 vs. Tampa Bay

After spending their No. 2 overall pick and a large percentage of free-agent money on defensive players, defensive coordinator Robert Saleh had a lot of pressure to deliver a lock-down defensive performance against the Buccaneers’ offense on Sunday.

Man oh, man did Saleh deliver. San Francisco’s defense allowed only 10 points to Tampa Bay, but scored 14 points on their own, thanks to a pair of pick-sixes from corners Richard Sherman and Ahkello Witherspoon.

The 49ers’ defense registered three sacks, on pace for 48 sacks this season — compared to the 37 sacks they had last season. San Francisco’s defensive backs already have one more interception this season than they did last year.

As the 49ers head to Cincinnati, trying to improve their record to 2-0, here are three things we’ve learned about Saleh’s unit.

1. Corner Ahkello Witherspoon’s sophomore slump is officially behind him.

Third-year corner Ahkello Witherspoon ended any hopes that the Buccaneers had on Sunday, returning an interception to the end zone and celebrating on Tampa Bay’s grave.

The former Colorado defensive back’s highlight of the afternoon was the pick-six, but that won’t solely define how great Witherspoon was on Sunday. He routinely was matched up against Buccaneers’ No. 1 receiver Mike Evans and ended the afternoon with three huge passes defended. Per Pro Football Focus, Witherspoon was also the highest-graded 49ers’ defender, with a grade of 80.8.

With corner Richard Sherman locking down one cornerback spot, the other spot was up for competition in the offseason, but it seems like Witherspoon has a fantastic grasp of it already.

2. Defensive lineman Nick Bosa — if healthy — will win DROY.

While the media and fans were critical of defensive lineman Nick Bosa for missing all of the preseason with a high-ankle sprain, tossing around the oft-used “injury-prone,” Bosa came out with a vengeance on Sunday.

The former Ohio State defender finished Sunday with one sack and six pressures against the Buccaneers’ offensive line. Per Pro Football Focus, Bosa also had a pressure rate of 28 percent, meaning he beat his blocker on 28 percent of snaps — a number that was the highest among defensive players in Week 1.

Bosa was routinely in the backfield, wreaking havoc and disrupting Bruce Arians’ offense. Quarterback Jameis Winston avoided Bosa in two instances. Otherwise, the rookie would likely have a few more snacks on top of his Week 1 total.

3. Safety Tarvarius Moore has placed his stake in the starting role.

The competition for the starting free safety position was wide open when training camp started. Second-year defender Tarvarius Moore, safety Adrian Colbert and safety Jimmie Ward were all in the mix, but as preseason wore on, it became obvious that Moore should be the starter.

The 49ers’ front office released Colbert and saw Ward get injured during practice, making their choice even more obvious. Moore had eight tackles on Sunday, one behind team leader Fred Warner. The second-year safety should have had an interception against Winston in the end zone, but had it slip through his hands.

Moore’s athleticism has been his biggest advantage, as he can cover a lot of ground and close the gap on receivers in a short amount of time.

The young guns on the 49ers’ defense impressed and it will be fascinating to watch how they continue their defensive performance against the Bengals on Sunday.