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The secondary is a concern for the 49ers, but it didn't look like one against Denver.
Cornerback Perrish Cox led the way for the group, which did a spectacular job Thursday. The outside linebackers also did a nice job, piling up a stellar 3.5 sacks. Backup linebacker Dan Skuta came through with two of those sacks, and outside linebacker Parys Haralson tallied one.
Oh, and starting outside linebacker Aldon Smith almost brought down Manning in his only series.
The outside linebackers harassed Broncos backup right tackle Vinston Painter, and as a result, backup quarterback Brock Osweiler was under pressure all night.
The secondary benefited from the pressure, and it turned in a gem of its own. Cox picked up five tackles (and one tackle for loss), and he shined on special teams as well. He returned one kickoff for 33 yards, and he returned a punt 15 yards.
Cornerback Tramaine Brock held star receiver Demaryius Thomas to just a seven-yard catch, and he also shut down deep threat Tavarres King. As for the safeties, Eric Reid did a great job tackling as he recorded six tackles. Special teams ace and starting safety candidate C.J. Spillman also impressed by electrifying Candlestick Park with some boisterous hits.
San Francisco did a fabulous job on defense, and the secondary and linebackers led the way. The secondary isn't laden with stars, and there isn't much depth at middle linebacker, but neither issue plagued the 49ers Thursday.
And luckily for them, that could be an indicator of much-needed future success at both positions.