Wednesday's 2-0 defeat by Celtic means the 45-year-old German has lost both matches in charge since succeeding Craig Levein.

Hearts remain second bottom and winless in six games, but there were positive signs against the league leaders.

"I think you could see improvements," Berra, 34, told BBC Scotland.

"Let's be honest, it's not going to be a quick fix. He just wants everybody to be a bit more aggressive when we're closing down, take more risks and, when we get the ball just play, don't be scared."

There was evidence of the high-pressing game Stendel employed at Barnsley as Hearts made a fast start against Celtic at Tynecastle before being stung by two goals in 12 minutes before the break.

But, despite the sucker punch, Hearts continued to cause the champions some problems, while also looking vulnerable to the counter attack.

"Sometimes we'll get caught, but he's not so fussed if you give the ball away sometimes," Berra said of Stendel's coaching.

"He's very demanding at the same time, but he knows you're going to give the ball away sometimes when you take risks. And we will be prone to giving up chances as well if you're going to play like that."

Next up for Hearts is a trip to face Hamilton Academical, who are the only side below them in the Scottish Premiership.

The teams are level on points, which means victory for one will isolate the other at the foot of the table ahead of Hearts facing city neighbours Hibernian.

"It's a massive game, a tough venue to go to," Berra added. "We'll go there with the same mentality - we'll have a go.

"After that, it's the derby. It's about getting points on the board, there's still a long way to go, but we want to build confidence and get a couple of wins out of these next three games."