Leeds boss Marcelo Bielsa admitted to sending an employee to watch the Rams train before the two sides met in January as the Whites ran out 2-0 winners at Elland Road.
The club were subsequently hit with a £200,000 fine by the EFL.
This is the fourth time in the last six seasons that Derby have been involved in the play-offs – and they are the form team having lost only one of their last 12 games.
Lampard said: “The fact that we’ve been on a good run has to be put to the side because the league is now done and we have to focus on these two games.
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“Very quickly in the week we turned our attentions to what’s coming and the huge games against Leeds.
“We mustn’t forget the fact they beat us twice, we mustn’t forget the fact that they finished (nine) points above us in the league.
“I respect them hugely, but we focus on ourselves and we’ll be ready.”
Leeds scuppered their chances of automatic promotion after losing five of their last nine league games, including a final-day defeat to bottom club Ipswich.
Now, Bielsa will be looking to reach the club’s ‘goal’ and end their 15-year exile from the Premier League via the play-offs.
Bielsa added: “We analysed deeply the last four games but we did that on the first day of the week.