Like many other fans, I've been worried by the recent defensive problems. After the jump, I'll analyze some of the issues. I also have a poll.
It's a little hard to explain what is going on with Patrick Ianni and Jeff Parke in the middle. They were so successful for most of last season, but since the injury to Jhon Kennedy Hurtado against Portland, they haven't been as sharp. If I recall correctly (and I didn't look at the stats), Ianni and Parke had a little trouble in their first few games together last season. Everyone knows that a successful center-back pairing requires good chemistry, and I think Ianni and Parke just haven't yet found that this season. Both are good, solid defenders that could start for most teams in this league, but on a championship-caliber team, each would be a "second center back", meaning their CB partner is a little stronger than they are. Having said that, both Ianni and Parke would be among the league's elite "second CBs". The (hopefully soon) return of Hurtado should help return the central defense to its usual prowess.
It's pretty clear the reason Tyson Wahl and James Riley are with the team is because of their offensive skills, and less so about their defending, which, until lately, has been more than acceptable on most occasions. I don't usually have problems with two offensive-minded outside backs, unless something is up with your central defense, as is the case currently for the Sounders. When your best defender is injured, your outside backs need to think less about offense and more about defense.
Although once a strong supporter of Riley, his appeal has started to wear off on me. I credit him for being one of the most fit guys on the team, as shown by the fact that he has played practically every minute this season. In the past, I've had few problems with his often attack-minded game, but we currently need him to be a stronger defender. Mauro Rosales crosses an excellent ball, often from near the endline; there is no need for Riley to try to overlap Rosales on his runs up the flank. Also, I consider Riley to be the "second anchor" of this defense behind Hurtado, so with Hurtado out, I feel that Riley should captain the back line. To do so effectively, he need not get caught up in the attack much, if at all.
Although it may surprise some, I really enjoy Tyson Wahl and his game. Like many, I think Wahl is a stronger soccer player, while Leo Gonzalez is a better left back, per se. Wahl swings in an excellent, left-footed corner, and showed his free-kick ability against New England. On most occasions, he has been able to hold his own at left back, although he looks shaky at times. I feel that the current left back on this team must be a part of the attack, because Alvaro Fernandez, unlike Rosales, is involved more in goal-scoring than crossing into the box. That said, Wahl must understand that without the best defender on the field, he can't get caught too far forward--nobody can rescue him if there's a problem.