The Cardiff Blue set up Shane Williams' crucial second-half try after taking over from injured full-back James Hook.
"Leigh's had his injuries and stuff, but he's a great professional and he... was a threat," Phillips said.
Phillips was also happy to "win ugly" against a nation who beat Wales at the 1991 and 1999 World Cups.
After an opening 17-16 defeat by South Africa, victory in coach Warren Gatland's home town of Hamilton has kept Wales on course for a possible quarter-final against Ireland, who beat Australia 15-6 in Auckland on Saturday.
Wales trailed Samoa 10-6 at half-time but buckled down after the break to slowly overhaul Samoa in a bruising Pool D encounter.
The crucial moment came when Halfpenny, who had come on at the start of the second half because of Hook's shoulder injury, stood under a high ball.
Samoa's chase was good but somehow Halfpenny wriggled between three tacklers to race up the left wing.
He found Jon Davies in support and although the centre's pass went to ground, Williams was on hand to sweep up the loose ball and go over.
In the process Wales' all-time record try-scorer became Wales' leading World Cup try scorer, his eighth touchdown surpassing the seven scored by Ieuan Evans and Gareth Thomas.
"The sun was low, and when Jonathan gave that pass the sun was right in my eye-line and I just lost the sight of the ball," Halfpenny said.
"But Shane was behind me and he went in at the sticks. Thankfully, Shane was there in the right place at the right time.
"It won the game for us, and all credit to Shane for working hard to get to the ball."
Wales failed to reach the performance level of the opening defeat to the Springboks, resulting in a sense of disappointed among the players despite the all-important win.
"It was great to get the win, but it was frustrating for us," said Phillips.
"I think we missed a clear chance in the first half and it could have been a different game then.
"It was frustrating because we didn't quite get the scores we should have had in the first half. I think we showed great quality to come back and win the game.
"We gave them so much respect in our preparation, but we weren't quite clinical and these things make or break a game.
"We just wanted to get the win, so be it being ugly or whatever - we just had to get the win."