Arsenal manager Arsene Wenger says heavy away defeats at the hands of title rivals derailed his side's Premier League challenge.
The Gunners suffered big losses at Manchester City, Liverpool, Chelsea and Everton, letting in 20 of the 41 league goals they have conceded this season.
"In some of these games, at the start, we were caught by surprise," he said after Sunday's 1-0 win over West Brom.
"We were perhaps too cautious. We paid a heavy price for it."
Wenger, who also cited injuries as a reason for his side's decline in the second half of the season, added: "We are frustrated because we were top of the league for 128 days then dropped off.
"If you look at the top of the table today then you see it's very tight. Then the matches where we dropped points enter your mind."
Arsenal lost 6-3 at current leaders City in December, but remained at the summit for much of the following month before the decline began.
The Toffees briefly overtook Arsenal in the race for fourth, but their defeat by Manchester City on Saturday was their third loss in four games and sufficient to guarantee Wenger's side another top-four finish even before the victory over the Baggies.
"To be brutal, we missed a few goals compared to some of the top teams who have scored more, while in some games we haven't been ready at the start and lost the game before we got going," added the Frenchman, whose side notched their fourth successive win.
"If you look at our overall performances, we've done well in the cups and the Champions League. We didn't fail anywhere. But we missed something to be decisive in the Premier League."
Wenger, who has been at the club since 1996, has yet to sign a new deal at the Gunners, with his current contract set to expire in the summer.
He reiterated that he would discuss a new contract after his team have played Hull in the FA Cup final on 17 May.
"I told you many times that my word is my word. I am from a period where you did not need a pen to commit," said Wenger.