Unai Emery will hope a return to the Europa League this week serves as the spark plug that ignites Aston Villa's season, while Nottingham Forest embark on their first European campaign in 30 years.
Emery is the most successful manager in Europa League history, winning the title three times with Sevilla and once with Villarreal, but his Villa side have made a troubled start to the new campaign.
Villa are winless through their first five Premier League games and had failed to even score before Sunday's 1-1 draw at 10-man Sunderland, which left Emery "frustrated and disappointed".
"Our start, we've not been doing well," admitted the Spaniard, who also took Arsenal to the Europa League final in 2019.
"There is still work to do; some players are adapting in the squad and our idea, and they will need time.
"Other players were here last year and know how we want to build the team and how we were being successful in the last three years."
Villa reached the quarterfinals of last season's Champions League before losing 5-4 on aggregate to eventual winners Paris Saint-Germain.
They missed out on qualifying again for Europe's top club competition on the final day of last season, with this their first appearance in the Europa League main draw since 2008-09.
Villa begin at home to Bologna on Thursday in a repeat of their 2-0 win over the Italians in the Champions League last October.
Bologna have qualified as winners of the Italian Cup, their first major trophy since 1974.
Like Emery, Nottingham Forest's new boss also knows what it takes to win the Europa League.
Ange Postecoglou, appointed by Forest earlier this month, steered Tottenham to a rare trophy last term as they beat Manchester United in the final.
He is searching for his first win at Forest following two defeats, including an early League Cup exit, and Saturday's 1-1 draw at Burnley.
BETIS TEST FOR POSTECOGLOU'S FOREST
The Australian, sacked by Spurs in June after their worst Premier League season, took over from Nuno Espirito Santo and is trying to implement his more expansive style at Forest in the quest for silverware.
"I do like my teams to play exciting football and score goals," Postecoglou said upon his arrival at the City Ground, the home of the 1979 and 1980 European Cup winners.
"No apologies about that. That's just the way I am and the way I want to see my teams play."
Forest travel to Real Betis on Wednesday for their first European game since the quarterfinals of the 1995-96 Uefa Cup against Bayern Munich.
Betis have former United winger Antony in their squad after the Brazilian rejoined the Spanish side on a five-year deal following a successful loan spell.
Led by former Manchester City and West Ham boss Manuel Pellegrini, Betis finished runners-up to Chelsea in the Uefa Conference League last season after reaching their first European final.
Celtic and Rangers both dropped into the second-tier competition after falling short in the Champions League play-off round last month.
Brendan Rodgers takes his Celtic team to Serbia on Wednesday to face Red Star Belgrade in a battle of former European champions.
Embattled Rangers are off to their worst domestic start since 1978 and fans protested against manager Russell Martin during Saturday's League Cup win over Hibernian, which did little to quell the anger felt around Ibrox.
"I can't control any of it," Martin said, as fans delayed the game by hurling hundreds of coloured balls onto the pitch and called for his sacking.
"At this football club, it becomes about one person really quickly," added Martin. "It's become about me, not by my choice."
Two-time winners Porto and Feyenoord, coached by former Dutch star Robin van Persie, are both competing in the league phase. Porto start against Salzburg while Feyenoord visit Braga.
Twice runners-up Roma open their campaign against Nice, while Fenerbahce – who sacked Jose Mourinho after failing to make it to the Champions League – are away to Dinamo Zagreb.