The biggest issue with the Cubs injuries is that it takes them out of their ideal platoon situations. When used effectively, the Cubs don't really have any weaknesses.
The biggest weakness hitting is at Catcher, where Soto is hitting .225/.319/.412. Not terrible for a catcher, above average for the position. Soto is better than that but that's what he's done so far.
Byrd, Soriano, and Ramirez shouldn't be platooned. They aren't ripping the cover off the ball but here are their triple slashes before today:
All solid but not spectacular. Ramirez especially is better later in seasons typically.
At second, Dewitt has been bad so far this year vs righties but I think he'll pull out of it. Barney has been fair, but has hit lefties especially good at .321/333/.396. I suppose I would stick with Barney most of the time and his .294/.314/.343 overall line. Fair enough stats for a very good defensive second basement. Dewitt might get it turned around in the future.
There is no platoon at first base, but their should be as Pena is hitting .265/.386/.512 vs righties and complete suck vs lefties, while Baker is hitting .433/.443/.617 vs lefties and complete suck vs righties. This platoon would be equivalent to the best hitting first basement in the game.
Right field is the other optimal platoon situation. Fukudome is doing good overall, and so is Reed Johnson, but vs their opposite throwing pitchers, Fukudome is hitting .283/.399/.390 and reed Johnson is hitting .375/.405/.550. That's a near-star level of production.
This would have resulted in 2 great hitting positions at 1B and RF, and going forward I think 3B will join that group. 4 average or above hitters at positions of SS, 2B, LF, and CF. Catcher lags behind but could be in the average or even the great group going forward.
Despite all the injuries, the Cubs have scored a fair amount of runs per game. Without the injuries I think they'd be on of the top scoring teams. Additionally, hitting is contageous, when some of the team hits better, it helps the rest of the team.