West Ham manager Manuel Pellegrini has challenged Felipe Anderson to improve further, despite the Brazilian scoring twice to see off Southampton.
Anderson, 25, grabbed both goals as the Hammers came from behind to beat the Saints 2-1 on Thursday.
That takes his Premier League tally up to eight since his £36m move from Lazio in July, but Pellegrini felt Anderson could still offer more to his game.
"He loses too many balls - he will continue improving," said Pellegrini.
"He must understand the Premier League is difficult if you keep the ball at your feet. He is a different player, a player that in every game makes important plays.
"His run of goals is important for him and the team. It's not easy for a midfield player to score so many goals by this stage of the season. He can change the score of the game in any moment."
Anderson has scored seven times in his past nine West Ham appearances, after netting only once in his opening 12 games in all competitions for the club with the Hammers ninth in the table at the halfway point of the season.
Pellegrini maintains unbeaten festive run
Pellegrini has never lost a match in the Premier League played between 26 December and 4 January. The win over Southampton means the Chilean, manager of Manchester City from June 2013 to June 2016, has now won eight and drawn two of the 10 games he has been in charge of during the festive period.
Liverpool boss Jurgen Klopp has won eight, drawn one and lost one in the same timeframe in England, with ex-QPR and Tottenham boss Gerry Francis also never beaten in this post-Christmas period.
Hasenhuttl unhappy with Saints errors
The match was the fourth game in charge of Southampton for Austrian Ralph Hasenhuttl, who replaced the sacked Mark Hughes earlier this month.
Hasenhuttl has now won two and lost two of those games and told BBC Sport: "The way we lost it was too easy, we didn't play such a good game.
"If you give it away like we did then you don't deserve to win. We were not so fresh and not so speedy, [or] sharp to win the second balls.
"Their goals were too easy, one from outside the box and one from a corner we had."