With deals for Ousmane Dembele and Philippe Coutinho reportedly high on Barca's list of priorities, Deulofeu's place in Valverde's side seems far from secure.
However, the winger did his first-team chances no harm with a fine individual display - setting up two goals in the space of three first-half minutes to put the game beyond Betis before the interval.
A year to the day since Barca's 6-2 victory in the corresponding fixture last season, Deulofeu crafted Barca's 36th-minute opener with a wicked cross that Betis defender Alin Tosca turned into his own net, though it was initially unclear as to whether Lionel Messi - who had already hit the post - got a touch.
There was no doubt over who got Barca's second, as Sergi Roberto slammed home from close range following fantastic work from Deulofeu, with Sergio Leon having squandered a great chance at the other end moments earlier.
Messi struck the upright twice as Barca looked to press home their advantage after the break, though despite his best efforts, Valverde's side put their Supercopa de Espana woes against Real Madrid behind them with a comfortable victory.
Following a touching tribute to the victims of Thursday's terror attacks in the city, it was the hosts, donning commemorative shirts with 'Barcelona' replacing their names to honour those impacted by the incident, who started on the front foot - Deulofeu going close with a deft flick three minutes in.
Utilised in a central role in the absence of the injured Luis Suarez, Messi was the next to try his luck, but the Argentine could not hit the target after exchanging a series of quick passes with Sergio Busquets on the edge of Betis' area.
Barca's captain was at his best again soon after with a wonderful free-kick, only for the woodwork to come to Betis' rescue, but the hosts would not be denied for much longer.
Messi played a neat pass into Deulofeu, whose first-time cross deflected in off the unfortunate Tosca.
That lead should have been short-lived as Leon got through on goal, but the striker's hesitation enabled Javier Mascherano to get back with a remarkable challenge.
Barca wasted no time in making Betis pay, Deulofeu easily getting the better of Betis new boy Zouhair Feddal before sliding in a cross to Roberto, who made no mistake with a composed finish.
Messi continued to cause havoc through the centre, and he went agonisingly close with a curling strike that clipped away off the left-hand upright.
Deulofeu received a standing ovation when he made way after 72 minutes, before his replacement Aleix Vidal was denied an immediate goal by Betis goalkeeper Antonio Adan.
Determined to get off the mark, Messi rattled the post for a third time late on, but the 30-year-old was unable to find the net as Barca had to settle for a two-goal cushion.
Key Opta stats:
- Barcelona have won each of their nine opening games in LaLiga. Barcelona’s last defeat in a season opener in La Liga came in August 2008 against Numancia, which was the first league game managed by Pep Guardiola
- Leo Messi has hit woodwork three times in the same game for the first time in the Spanish League.
- Sergi Roberto has scored his first league goal for Barcelona.
- Gerard Deulofeu has provided 20 assists since 2013-2014, the second most for a Catalonian player on the top 5 European Leagues after Cesc Fabregas (50).