There are needs elsewhere—a touch more creativity in midfield and perhaps another option in defence—but nothing comes remotely close to the concern in attack.
Roberto Martinez's side face an especially crammed schedule this season, bloated by additional Europa League commitments. The Toffees may well play over 50 games and, at present, carry few alternatives to lead the line in place of Lukaku.
Both Kevin Mirallas and Steven Naismith can, and presumably will do a job in attack, but both have proven themselves far more effective buzzing in and around a front man.
Elsewhere, Arouna Kone hasn't kicked a football in competitive action for almost 11 months and still seems some way off a full recovery. At 30, whether or not he's able to recapture his best form must remain a doubt. Looking further down the roster, the only other alternatives for Martinez are fresh-faced academy prospects.
The fall in quality from Lukaku down to anything else at the Catalan's disposal is substantial and far too much of a risk to carry through to January.
Lukaku scored or assisted 21 of his side's 61 Premier League goals (34 per cent) last season and his importance was emphasised by Everton's return with and without him.
With the powerful Belgian in the team, Everton scored 56 goals in 31 games at an average of 1.8 goals per game. Without him, albeit in a small sample size, the drop was significant; Everton scored just five times in the seven game he missed (0.7 goals per game).
Unsurprisingly, Everton also averaged far more points with Lukaku on board, taking over two points per game in the 31 games he featured in—a ratio good enough for the Champions League. Without him, the Toffees took just nine points from seven games.
Everton must find a striker to reduce that gap.
Lukaku will be needed for the majority of games, but in such an elongated season, relying entirely on one striker bought in exchange for most of your transfer budget is asking for trouble. Any kind of injury for the Belgian would quickly jeopardise Everton's entire campaign.
This is why a strong second option must be found. A player who can not only deputise and make the loss of Lukaku less glaring, but who can also provide a genuine threat from the bench.
Martinez is currently without any manoeuvrability if his side are chasing a game and would prefer keeping Lukaku fresh to start 35 games instead of flogging him with 50.
Entering the home straight of the summer transfer window, Danny Welbeck and Samuel Eto'o are two names currently linked, per The Express' Paul Joyce, while Lacina Traore is presumably still an option following his short stint last season.
As Everton tackle a testing Thursday-Sunday schedule, there will be regular rotation throughout the side. Presently, any such switch in attack provides too much of a handicap to justify.
Statistics via WhoScored.com.