First-team defensive notes vs. the Broncos

For the record, the Broncos played without starting running back Monte Ball, left tackle Ryan Clady and linebacker Von Miller.

– Tony Jerod-Eddie and linebacker Michael Wilhoite held running back Ronnie Hillman to a 2-yard gain by fighting off blocks and converging on the runner. Impressive.

– Safety Eric Reid did not know whether to plaster receiver Wes Welker or to play the ball on a 15-yard pass to Welker over the middle. Stuck between the two, he allowed Peyton Manning to complete the pass. If Reid played the ball, he might have intercepted the pass.

– It looked like some 49ers were playing man and others were playing zone on a 20-yard completion to Damariyus Thomas that put the ball on the 49ers’ 10. Jimmie Ward and Perrish Cox ran into each other on the play.

– Cornerback Perrish Cox put on eight pounds of muscle over the off-season and it shows. He made a tackle in space on Thomas and forced an outside run inside by fending off a block with impressive leverage.

– Don’t know why Chris Culliver was playing 10 yards off the ball on 2nd-and-5. It allowed an easy completion from Manning to Thomas for a first down.

– Rookie linebacker Chris Borland just gets run over at times by offensive linemen. However, he remains really active. By contrast, Michael Wilhoite plays more tentatively, but seems more assignment sound. If things keep going as they are between these two, Wilhoite would have to be the starter because Borland simply makes too many mistakes.

– 49ers’ zone defense is too loose, with huge gaps that Peyton Manning exploited during the Broncos’ second drive.

– The coverage is also making mistakes. On the 17-yard touchdown pass to Julius Thomas, three 49ers — Eric Reid, Jimmie Ward and Perrish Cox — covered one receiver to the right, leaving safety Craig Dahl with no help in the middle.