Slaven Bilic has backed new recruit Dimitri Payet to "make every player better than they actually are" at West Ham.
Hammers boss Bilic hailed the £11 million summer capture from Marseille as his "number one target" but admitted he will chase two more Upton Park additions.
France playmaker Payet is set for his full competitive debut as West Ham host Astra Giurgui in Thursday night's Europa League third qualifying round.
The former Croatia manager conceded West Ham cannot hang fire on transfer plans while they fight to secure European football for the season ahead.
"It's still early days but Dimitri it's not only my opinion but I know so far he's not only a great player, he's a great professional, he's a good lad," said Bilic.
"He has mixed already. He's the kind of player I thought we really needed, that's going to make every player better than they actually are.
"He's got everything. He likes to take responsibility.
"He was my number one target and I am grateful to chairman that we got him. And it was done like that -- not in four weeks.
"He's doing really well at the moment. Not only him but all the guys but you ask about him.
"It may go a bit up and down. But we're going to help him and he's going to help us."
Bilic remains confident West Ham can yet complete a permanent deal to bring Barcelona midfielder Alex Song back to Upton Park for the season ahead.
Former Arsenal star Song spent last season on loan at West Ham but faces three months on the sidelines with ankle trouble.
The 27-year-old is locked in negotiations over the length of a potential Hammers contract, with Barcelona ready to let him leave on a free transfer.
West Ham have also been linked with a £12 million bid for Fenerbahce striker Moussa Sow -- with Bilic refusing to bide his time as he seeks further squad improvements.
"That is very tricky because you can't wait that long," said Bilic when asked if securing Europa League football would boost West Ham bargaining power.
"So we will have to risk one way or another.
"Like any other manager you put your players on the sheet and you go 'we are ok, we are ok'.
"But considering that this is the Premier League and we might play in Europe and the Premier League is very tough and very long then of course I would like to have one or two.
"But we are not talking about five, six, seven or whatever.
"I am happy with my team and squad, we might need one or two.
"You have to spend. You have to be clever of course but even Einstein would have to spend money.
"So of course there is a budget and fair play so you have to calculate and do it.
"I have done it with big help from the chairman and the board and the scouts and my staff.
"We bought really good players. We didn't buy players to just add numbers."