Lawes had not played since injuring his knee in the loss against Sale Sharks on November 1, but he was able to finish the game at Stade Yves-du-Manoir.
And that was a positive for Saints, who have been short of the likes of Calum Clark and Tom Wood in recent weeks.
“It’s a big ask to go into a game like that when you’ve been out for six weeks and not really done too much running,” said Mallinder after his side’s 33-3 Champions Cup defeat.
“It’s been a knee injury so clearly his fitness will improve the more games he played.
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“We’re pleased to have him back.”
Lawes, typically a lock, started the game at six.
And Mallinder feels he performed well in the position.
“He’s played a little bit on the flank for us before, but second row is probably still his best position,” said the director of rugby.
“He gives you a very good lineout option, he’s good around the field and he put in some cracking tackles, particularly in the first half, so we’re pleased with his performance.”