U.S.' John Brooks 'a diamond' at the back - Hertha Berlin's Pal Dardai

John Brooks has been praised as a "diamond" by his Hertha Berlin coach Pal Dardai, who urged the United States international to become more consistent.

Although contract talks between the club and the defender have reportedly stalled, Brooks secured Hertha's 2-1 win over Bayer Leverkusen on Saturday with a header following a Marvin Plattenhardt corner.

Dardai said Brooks has moments where he shines but added that the 22-year-old needs to be more consistent.

"Tension is the key for him. If the tension's right he's a diamond," Dardai said.

Club captain Fabian Lustenberger also praised the performance of Brooks, who played alongside the Switzerland international at centre-back.

"You could once again see what a great footballer he is," Lustenberger said. "When he can access his potential, he is an outstanding centre-back."

The Berlin-born U.S. defender has had difficulties reaching his full potential in the past, and the club's sporting executive Michael Preetz told Berliner Morgenpost he'd love to see Brooks hit the back of the net more often.

"Great goal," Preetz said. "But with his abilities he could score four or five goals in season."

Meanwhile, kicker reported that contract talks between Brooks and Hertha have stalled. The defender is under contract until 2017, and after changing agents earlier this year no breakthrough has been made in the talks.

Hertha's fifth home win of the season saw Dardai's side move up to fourth in the Bundesliga table, a position that would qualify them for the Champions League playoff round next season. But Lustenberger said their current position is "only a snapshot."

"Maybe it'll last until the end of the season, but two years ago we had 28 points after the Hinrunde [first half of the Bundesliga season], and end the season with 41," he said. "We are warned."