These have been a valuable few days for Eagles defensive coordinator Jim Johnson. He has looked every which way at his defense, which has been as up-and-down as any he has had in Philadelphia in a six-game stretch. At times, the Eagles have been absolutely dominating. They have forced turnovers. They have scored points. They have overwhelmed the line of scrimmage.

And at other times, they have been puzzlingly bad. The run defense has been gashed. Tight ends are having their way in the passing game. One or two times the deep coverage has faltered, allowing big passing gains down the field.

Johnson has seen all of that over and over and over this week. In his days of self-scouting the defense, Johnson has re-evaluated the approach, the personnel and the execution through six games.

And he has no doubt concluded that the defense has to make some adjustments moving forward. You think halftime tweaks are important? Yeah, sure, but Johnson has had a week-long halftime to make things right with his defense.

"You look at everything," Johnson says. "Good and bad. Evaluate everything. I'm sure we'll see a few things change, but I like a lot of what we've done defensively."

For the most part of the season, the Eagles have been outstanding stopping the run. They have picked the right time to blitz, they have tackled well and they have played on the other side of the line of scrimmage. But in back-to-back games against Washington and then San Francisco, the run defense sprung leaks. Washington ran at the edges and controlled the line of scrimmage on the way to 201 rushing yards. San Francisco was able to blow open a few holes and give running back Frank Gore some big runs through three quarters of last Sunday's game.

"After that, though," said Johnson, "we got after them. I liked seeing that. I hope it is the way we play the rest of the season."

Johnson isn't going to tinker too much with the personnel. He has to get his tackles, Mike Patterson and Brodrick Bunkley, back in the game against the run. In those first four games, the tackles chased down ballcarriers and were a force against the run. Johnson said then that there was "not a better pair" of tackles against the run than Patterson and Bunkley.

The perception changed against Washington, as the Redskins got to the edges and then cut back and made big gains on the ground with Clinton Portis. Was it a technical breakdown, a series of personnel mistakes or a combination?

Johnson said in the days afterward that it was a combination of all of the above, and then some. Perhaps, then, it was a one-game step in the wrong direction. However, when the 49ers came out and controlled the ball through three quarters in San Francisco, there was reason for concern.

That the Eagles rose up and shut down the 49ers in the fourth quarter was encouraging.

Still, Johnson has some things to figure out. The Eagles need to be better when they are in the nickel -- both when they rush the quarterback and when they have to stop the run. The production from opposing tight ends is a real problem that Johnson has to fix. While some blame Chris Gocong, the strong-side linebacker, the truth is that Gocong played about a dozen snaps in San Francisco and is the linebacker to come off the field in the nickel, when much of the damage is done.

One of the best coordinators in the game, Johnson knows he has a lot to work with here. The things to watch when the Eagles resume play are many. Here is my list ...

• Pass rush from four-man front. Juqua Parker is having a terrific season. Trent Cole is playing well. Darren Howard has been much better than at any time in his Eagles career. The Eagles need to see if Chris Clemons -- who played a decent amount in San Francisco -- can help them get to the quarterback without having to bring extra pass rushers.
• Better play when in the nickel. Victor Abiamiri is on the field inside at tackle in the nickel and he has to be a plus here. Has to. The Eagles need him to play well against the run and get some push when rushing the quarterback.
• Stop tight ends. This is probably more of a scheme adjustment than a personnel adjustment, because the Eagles are leaving tight ends wide open. Something is happening in the coverage X's and O's that Johnson has to fix.
• Stop the run. The Eagles have done a good job on first downs in their six games. They are giving up too many big runs, too many third-down runs. Is Johnson willing to risk it and blitz more against the running game?
• Continue to take the ball away. The Eagles have done a good job in the takeaway department. They must remain aggressive and take advantage of the opportunities they have to force turnovers.

Johnson will have some different things in the works when the Falcons come to town, and then he will have more changes for the Seahawks and the Giants and so on. And make no mistake: While there is so much attention on the offense and the ups and downs there, it is the defense that must lead the way into the playoffs and beyond. The Eagles have some pieces to put in place on that side of the ball to get Johnson's house in order for the stretch run.