I think it goes on minutes played as well as just bodies lost.
CB we lost Sol Bamba (1900) minutes, Lee Peltier (1000 minutes), Grant Hall (700 minutes) and Nathan Wood (180 minutes).
Darragh Lenihan played 3500 minutes in CB for Blackburn, and with Fry, McNair and Dijksteel playing a lot more minutes than any of the above, and Marc Bola as cover - we're probably good here.
RWB we lost Djed Spence's 300 minutes and Lee Peltier's 300 minutes - We have nobody to cover here so we definitely need someone. Tommy Smith played 2400 minutes here for Stoke.
LWB we lost Neil Taylor's 1300 minutes Lee Peltier's 400 minutes - so Ryan Giles covers more than enough here, with Marc Bola as cover.
Midfield we've only lost Payero's 800 minutes and Toyosi Olusanya's 60 minutes, which can probably be replaced with Boyd-Munce and Hackney, although cover would be good here.
PLAYERS WE NEED - 5
3 Strikers
Tommy Smith - RWB cover - he can also cover for RCB in an emergency (like Lee Peltier did last season).
CDM - We only have Howson as CDM, although Hackney plays there and has had a good pre-season, he's probably not good enough.
PLAYERS THAT WOULD HELP - 2
Hayden Coulson - LWB cover - from the academy, low wages, wants to stay, I don't see any harm in giving him a squad position - having more LWB cover also puts Marc Bola as LCB cover.
CM (Squad Player) - Crooks, Tavernier, McGree and Boyd-Munce are enough, but if we have injuries we don't really have additional squad players here.