The Bees took the fight for promotion to the last game against Wigan with a superb 2-0 victory at Reading’s Madejski Stadium thanks to goals from Tarkowski and Alan Judge.
But their destiny is out of their hands as they need to beat the already-relegated Latics and hope the Royals can get over Saturday’s defeat and secure three points when they visit Derby.
It could also come down to goal difference as the Bees can also make the cut if Blackburn Rovers win against Ipswich Town, along with a three-goal swing going the Bees’ way.
Steve Clarke’s Reading are third-from-bottom in the form guide but will want to finish the season with a morale-booster at the iPro Stadium and Tarkowski is hoping for a favour from the Berkshire outfit.
He said: “Derby have everything to lose and we have everything to gain - the pressure is all on them.
“We have to play the best we can, but also make sure we get our goal difference back up as it could come down to that.
“A few weeks ago we would have been hoping to be already in there [play-offs], but results didn’t go our way. We still have a chance.”
He added: “Most of what has gone on has not been mentioned, and the gaffer has kept us away from it. Nothing has changed with him or David Weir.
“Even though the gaffer is not going to be here, there is still a big group of players and staff that want to make it into the Premier League.”
As well as getting himself among the goals at Reading, Tarkowski performed admirably at the back and helped the Bees defence keep their first clean sheet since February’s win over Blackpool.