"We had chances to qualify directly in the game against Albania, but we weren't good enough," Olsen told reporters, referring to the goalless home draw in early September, as he unveiled his 23-man playoff squad.
"We don't' have a player that will score ten goals in qualifying, so we all have to work very hard to put ourselves in that position and create chances, and obviously we need to be better at exploiting them," the 66-year-old added.
Nicklas Bendtner netted for his club Vfl Wolfsburg in a 2-1 home win against Bayer Leverkusen on Saturday, but the former Arsenal striker has struggled for playing time since moving to the Bundesliga after a barren spell on loan at Juventus.
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In contrast, Fischer was involved in four goals as Ajax thrashed Roda JC Kerkrade 6-0 at the weekend, scoring twice and helping to set up two more while contributing an inch-perfect pass in the build-up to a fifth.
Fischer, who last played a competitive international against Armenia in a World Cup qualifier in September 2013, scored his only international goal in a friendly versus Montenegro in June.
Denmark and Sweden meet in the first leg of the playoff at the Friends Arena in Stockholm on Nov. 14 with the second leg taking place three days later at Copenhagen's Parken Stadium.
(Reporting by Philip O'Connor; editing by Ken Ferris)
