The former Melbourne Victory man has labeled the New Zealand striker as 'priceless' and would hate to think what would happen if he wasn't at the club.
"He is priceless to us, as is Jason (Culina). We always know Shane will get on the end of everything. He's on fire at the moment and can do no wrong," said Pantelidis.
"What he's achieved so far this season is unbelievable.
"We don't want to think what it would like to be without him.
"Hopefully we won't have to find out anytime soon."
The comments come after Smeltz netted his ninth goal of the season, in the 90th minute, to give United a share of the points against Perth Glory after being two goals down on Sunday.
"That goal really summed him up," added Pantelidis. "He put his body on the line and made sure he got his foot in first and the ball was in the back of the net. That was pure Shane.
"It will be tough to hang on to Shane.
"Especially when the European transfer window opens. We just want to make the most of it while he's here and who knows what the future holds?
"He's by far the most dangerous player in the competition, but like any striker he needs good service and he gets quite a bit of that from the players around him.''