Jurgen Klopp believes Darwin Nunez has "arrived 100 percent” after the Uruguayan striker scored the winner for Liverpool against West Ham on Wednesday.

Nunez initially struggled following his move from Benfica at the end of last season for a reported initial fee of $72 million) that could rise to $96 million.

However, an all-action performance from the 23-year-old against the Hammers saw him score the only goal of the game with a header from a Kostas Tsimikas cross, while also forcing Lukasz Fabianski into a fine save and hitting the post among his six efforts on total from 56 minutes on the pitch, before being substituted as a precaution.

Nunez now has five goals in 12 games (six starts), and has netted three times in his last four appearances in all competitions.

"It is important. He has scored now a couple of times in the last few games. He arrived 100 percent, now even with numbers, which is fine," Klopp said at his post-match press conference. 

"He felt a little bit the muscles at half-time but it was all fine and after five minutes [of the second half] I was just a bit concerned about long sprints for him and balls where he stretches his legs. I thought, 'Come on, we cannot take that risk' and that's why we changed."

Despite having a number of chances to score again after Nunez's 22nd-minute goal, Liverpool came under pressure as David Moyes' men grew into the game, with Alisson having to save a penalty from Jarrod Bowen after the forward was brought down by Joe Gomez just before half-time.

The Reds held on for their second 1-0 win in a week, having beaten Manchester City by the same score on Sunday, and Klopp conceded it had been another tough three points to claim.

"It is a Premier League game and I cannot remember an easy game in all of the seven years and few days, and that was for sure not easy tonight," he said. "But we played well enough – and in moments, really good. In the end, all together, well enough to deserve three points.

"It's the second 1-0 in a row which is absolutely fine. It's a brilliant result... that we have space for improvement I think is clear, it was always the case and is tonight the case.

"But in this moment, we have three points more than before and that feels massive."