Injuries to Robin van Persie and Theo Walcott may force Arsenal to focus on defence rather than attack when they seek to dump Barcelona out of the Champions League and reach the quarter-finals on Tuesday.
Arsene Wenger's side produced a stirring comeback to win 2-1 in the last-16 first leg at the Emirates, when Van Persie and Andrei Arshavin struck late goals to shock a Barca team who let them off the hook.
Since that high, however, Arsenal have gone through the full gamut of emotions.
Their League Cup final defeat by Birmingham City blocked their easiest route to long-overdue silverware and after being given optimism in the Premier League title race by Manchester United's loss to Chelsea, were promptly held 0-0 by Sunderland.
Wenger was furious after his side failed to beat Sunderland and his mood was not helped by an injury to Jack Wilshere that threatens to keep the precocious midfielder out of Tuesday's clash.
Cesc Fabregas missed the Sunderland match with a hamstring injury but Wenger is optimistic he will be available.
While the absence of forwards Walcott and Van Persie is a blow, Wenger believes it is the efficiency of his team's defending that will be crucial.
Last year, Arsenal were crushed 4-1 in a Champions League quarter-final second leg at the Nou Camp, after a 2-2 first-leg draw, when an irresistible Lionel Messi scored all four goals.
"It will be very important for us to defend well because when you go to the most effective attacking team in the world, you want to have your best defenders available," Wenger said.
Barca have recovered from the defeat in London to string together four consecutive victories and consolidate their place on top of La Liga.
They have not conceded a goal in their last three outings, but they have lost the swagger they showed earlier in the campaign and must make defensive changes against Arsenal.
Captain Carles Puyol has failed to recover from a knee injury and with Gerard Pique suspended, coach Pep Guardiola, who is struggling with acute back pain himself, will have to field an unfamiliar back line.
"If we maintain our personality, we'll be halfway there," midfielder Xavi told the club's television channel. "We are at home, we are the favourites and with the help of our fans we'll get through to the next round."
AS Roma have undergone a dramatic transformation since losing 3-2 at home to Shakhtar Donetsk in the first leg of their last 16 tie and travel to Ukraine for the return in confident mood.
Roma have gained a new manager, won two matches, drawn one and lost one since their shock defeat last month.
"We must think about one game at a time and we're going to Ukraine to win," said coach Vincenzo Montella after Friday's 2-1 victory at Lecce.