Bouncing back from a loss in Minnesota in which some players felt they didn't show enough energy is one.
Defensive coordinator Vic Fangio on Thursday added several more: The Jets' ability to generate offense from multiple sources.
''They play a lot of different personnel,'' Fangio said before the 49ers practiced on the rain-soaked field at Youngstown State University.
''They've got a one-wide receiver offense. They've got a two-wide receiver offense. They've got a three-wide receiver offense. They'll play a lineman at tight end. They'll give you some unbalanced line. They'll give you the (Tim) Tebow package, which you have to prepare for, so they're very multiple," Fangio said.
Having linebacker Patrick Willis healthy will help. Willis, hurt in the 24-13 loss to Minnesota last Sunday, said his right ankle ''feels good.''
Willis praised the Jets' ''good receivers and big linemen,'' and is confident the 49ers are ready after ironing out a few problems that popped up in Minnesota.
''We know where we made our mistakes,'' he said.
Fangio took blame for not putting more pressure on the Vikings.
''We didn't execute as well as we're capable of executing and I could have had us in some better calls in certain situations,'' he said. ''We just didn't have our best day rushing the passer. It was a little bit of everything.''
The Jets feature a little bit of everything – with a large portion of speedy wide receiver Santonio Holmes.
''He's very explosive, he's fast, he's quick,'' Fangio said. ''He's very dangerous after the catch. Once he gets the ball in his hands, he's like a punt returner.''
If the 49ers do contain quarterback Mark Sanchez and the passing game, the Jets may turn to Tebow a little more in a wildcat formation.
Willis said defenders have been watching film of Tebow running it a year ago in Denver. Fangio said the 49ers worked against it a bit in training camp and have done more work this week.
''When you really have to go against it, you've got to change the way you play things and alter your play to compensate,'' Fangio said. ''You have to take it very serious.''
Meanwhile, offensive coordinator Greg Roman is losing sleep trying to analyze Jets coach Rex Ryan's complex defense. He apologized for being unshaven after the staff stayed up ''into the wee hours of the morning.''
Roman expects Ryan to concoct new schemes to counter the loss of star cornerback Darrelle Revis to a season-ending knee injury.
''I'm sure they are going to adjust somehow,'' Roman said. ''There's a lot of different ways they can do it and we might see all of them. We have to be ready for anything.''
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