I don't think that the wheels have really come off; we're still looking at only a four-game sample of subpar play, which happened to coincide with a couple important players missing out due to injury. Lambert misses the Doncaster game, we generate little going forward and lose. Davis misses the Blackpool game, and Bialkowski has a shocker. If they're fit for those games, there's a pretty good chance that we're talking about a draw against Donny and a win against Pool, at which point no one is biting their lips over our wobble.
That isn't to downplay the results...every team has injuries, and it's somewhat worrisome that we're so dependent on a short list of players, though we're not far from the transfer window. Rather, it's hard to draw any conclusion about upcoming results from the past four if those key players are healthy...if we struggle through December, the team's promotion hopes could be in trouble (January and February will be very difficult), but it's just as or more likely that they regain their footing and hit New Year's Day a few points clear of second.
In terms of additions, we definitely need another quality striker, because we're totally reliant on Lambert's brilliance at the moment...if he's out injured, we simply aren't the same team.
I'm not sure that wing is a major need, as Guly has (most of the time) acquitted himself fairly well there, and getting a striker would allow him to shift back to RW, rather than using central mids out wide as we're often doing now. Still, it wouldn't hurt to get one, especially if Chaplow's knee keeps him out for some time.
Beyond that, a central defender wouldn't hurt, especially one who can provide adequate cover at right back should it be necessary.
Basically, there isn't a major hole...if guaranteed perfect health, this team as constructed would suit me fine. But right now we're quite vulnerable to injury, as the past few games have demonstrated.