What to watch for: Vikings-49ers

The Vikings' third preseason game is tonight in San Francisco, and it will serve as the final look at almost all of their starters before they begin the season in Detroit on Sept. 8. It's no coincidence the third preseason game is on national TV -- if Adrian Peterson was going to play at all this preseason, it was going to be tonight, and the reigning MVP will give fans at least a little taste of what to expect this season. But for the Vikings, there are more pressing matters than what Peterson does in a brief tuneup.

Here are five things to watch from the Vikings' perspective:

1. Christian Ponder's last rehearsal: The Vikings' starting quarterback hasn't done much to ease fans' anxiety about how he'll perform this season, throwing an interception on his second pass of the Vikings' first preseason game and going 5-for-12 for 53 yards last week against Buffalo. He'll play into the third quarter tonight in his most extensive work with new receivers like Greg Jennings and Cordarrelle Patterson before the season starts, and it would help Ponder to show tangible signs of progress before starting his third season. Coach Leslie Frazier stopped short of calling tonight's game "crucial" for Ponder but did say it's important for the Vikings coaches to come off the field with some confidence about where the team is at in certain areas. Count Ponder's play high on that list.

2. More work for Patterson: With Jarius Wright staying home because of a concussion, Patterson will get his first work with Ponder in a game, and the Vikings could get some chances to see whether the dynamic rookie can take advantage of how defenses are playing Peterson. He hasn't caught a pass from Ponder in a preseason game yet, but that will likely change tonight, and the Vikings can take a look at how prominently Patterson can factor into their offense early in the season. It will be especially interesting to see if Patterson gets on the field with Jennings and what kind of production the Vikings can get with both receivers in the same packages.

3. A rebound for the O-line: The Vikings offensive line had some uncharacteristic mistakes last week in Buffalo; Matt Kalil missed a block on Jerry Hughes on the first play of the game, and John Sullivan delivered a shotgun snap before Ponder was expecting it, leading to a fumble that Ponder recovered. The unit was solid all last season, and tonight is a chance for it to clean things up against a strong defense. That's particularly important in pass protection, considering how much Ponder struggled under pressure last season and how much pressure the 49ers can generate.

4. "Good-on-good" action for Bishop: The Vikings will give linebacker Desmond Bishop plenty of work with their first team tonight so they can see how he fares in what defensive coordinator Alan Williams termed as "good-on-good" situations (in football parlance, the Vikings want to see Bishop against the 49ers' best players). As Bishop returns to his hometown, he'll also have an opportunity to make a strong statement that he deserves one of the Vikings' linebacker spots. That seemed to be a foregone conclusion when he signed with the team in June, but Bishop missed time in training camp and sat out the Vikings' first preseason game with a groin injury, and he's been playing behind Marvin Mitchell at weakside linebacker. Tonight, he'll be on the field quite a bit with the Vikings' starting defense, and, after playing last week for the first time since he tore his hamstring in the Green Bay Packers' 2012 preseason opener, Bishop has an important opportunity to show he's still effective at age 29. The Vikings have a number of young linebackers, like second-year man Audie Cole and rookies Gerald Hodges and Michael Mauti. That means there could be some hard decisions looming at the position, and Bishop needs to make his case after an up-and-down performance last week in Buffalo.

5. "All Day" at night: Even if it's only for a few carries, Peterson's presence on the field is hard to ignore -- particularly when he hasn't played since last January's playoff loss and when he figures to be prominently featured on TV. He has never carried less than than 10 times when he's played in the Vikings' third preseason game, though it seems likely he could get less work than that tonight. Still, Peterson fundamentally changes the Vikings offense. Defenses have to account for him, and Ponder will get his most realistic action of the preseason simply because of that fact. The Vikings could also see how other fullbacks, like Rhett Ellison and Zach Line, fare as lead blockers for Peterson with Pro Bowl fullback Jerome Felton out for the remainder of the preseason after an emergency appendectomy earlier this month.