The Tannadice side shocked a fancied Aberdeen on the opening weekend of the SPFL Premiership with a storming 3-0 win at Pittodrie, propelling them to joint top of the SPFL Premiership table along with Motherwell, Inverness and St Johnstone.
That result came despite losing two of their brightest stars of last season over the summer with left-back Robertson moving to Hull City and forward Gauld clinching a transfer to Sporting Lisbon.
However, McCall has been impressed by the men Jackie McNamara has it his disposal this year, in particular his forward group of Gary Mackay-Steven, Ryan Dow, Nadir Ciftci and Mario Bilate, who was brought in from Sparta Rotterdam last month. And the Motherwell manager is under no illusions as to how tough the task remains for his side tonight as they travel to Tannadice.
"I think they are stronger than last season," said McCall, who saw United put 14 goals past his team in one draw and three defeats last term. "Ryan Gauld is a terrific talent, has great ability and is a great prospect for the future. But even if you looked at Jackie's team at the back end of last season Dow was actually more effective for them and played in the cup final ahead of Ryan. And at left-back, I am hoping and am sure young Andy Robertson will go and represent Scotland for years to come but you miss a goalie, you miss your top scorer, but a left back?
"They are probably in the strongest position they have been in for a long, long time. You see Stephen Thompson say they don't have to sell. They have a group of players there at a good age and good strength in depth. I think they are as well equipped as any club to not threaten Celtic, but certainly be in that second position, along with Aberdeen obviously."
Motherwell were forced to go without the first-team trio of Steven Hammell, Simon Ramsden and Iain Vigurs for their opening day 1-0 win over St Mirren, with none of them ready to return for tonight's game.
McCall is still looking to strengthen his thin squad, however, with the Fir Park manager hopeful Derby County defender Mark O'Brien will join on a short-term loan by the end of the week, along with an unknown striker at some point soon after.
He said: "It's been documented that we are trying to bring in Mark from Derby. We might have had him earlier but he picked up an ankle injury on tour with them. He is now back in full training so we are looking to get him up at the back end of the week. He has not had a lot of game time but we would like to add him to the squad.
"In terms of a striker, we were hoping to get one of the young lads at Manchester City [believed to be Devante Cole, son of ex-Manchester United star Andy]. He is young, though, and his family want his first loan to be closer to home, which is perfectly understandable.
"We are still trying for a striker down another avenue. If it comes off then we will delighted. He would be coming on loan. We have been working on it for a while and we'd like to know by the weekend."
As McCall hopes for good news on the striking front by the weekend, United's Ciftci believes shutting the back door will be vital in their quest to finish best of the rest this season.
McNamara's side's opening-day destruction of Aberdeen was the first time they'd managed to keep a clean sheet since last December.
"It said a lot about our defending at Pittodrie that we didn't concede," said Ciftci. "But it's not just the back-four. We must work hard as a team and that was good on Sunday and we want to keep improving."