The 26-year-old was an unused substitute in Everton's last two matches, and has only played a combined 52 minutes in the three games prior.
Toffees boss Lampard admitted his focus remains on the relegation battle, but did urge the midfielder to fight for his opportunities.
He said: "I have had those discussions with him. He'll be very clear as to where I am and at the moment I'm much more concerned about the collective, getting over the line as a group.
"If Dele plays his part in these three games then great. He's come on at times and done good things for us. It's an area of the squad where we have other players that have been playing, that's just the reality of the situation.
"He needs to just keep training hard and stay really well focused and fight for the opportunity."
Everton's Premier League future remains in their hands, and a victory over Brentford on Sunday would secure their top-flight status for next season.
Lampard praised his upcoming opponents, saying: "Just a really good team. Full credit to them, the way that they play, they change style occasionally and they give you different threats.
"They're a hard team to analyse because of the flexibility they have in the team, which shows that they've got a very good coach and they deserve their status.
"They've worked hard for it and they've been on particularly good form in recent weeks. It's going to be a big challenge for us."
Everton are currently 16th in the table, having picked up seven points from their last three league outings.
Brentford, in contrast, are currently 13th but trail ninth-placed Brighton by just four points.