United began the three-match Scottish tour with victory at Greenock Morton on Wednesday evening.
In his homeland, David Weir began life as Blades boss and gave 22 players a run-out at Cappielow Park.
The only goal of the game came in the second half with Chris Porter converting a penalty after Febian Brandy was fouled.
United included three triallists - Danny Grainger, who has been released by Hearts, Steven Saunders, who is out of contract at Motherwell, and Roy Kayara, who is on trial for a couple of weeks from New Caledonia - and all were on the bench, whilst the home team's teamsheet included no less than eight unnamed triallists.
Of the summer signings, only McGinn started, slotting in alongside Doyle, with McDonald further advanced. Goalkeeper Howard was happy to get a couple of early touches after his long, enforced injury absence.
The Blades won four corners in the opening 15 minutes but clear-cut chances were at a premium early on. McFadzean was ushered away from a Westlake cross and McGinn's effort from outside the box was blocked.
For the home side, one of their triallists headed over a corner around the half-hour mark and, for the Blades, McDonald's shot was turned against the outside of a post by goalkeeper Caraux on 37 minutes.
Boss Weir sent out a completely different XI for the second half, including the triallists, newboys McGinty and Brandy, as well as teenage goalkeeper Willis.
The first effort of the second period, inside two minutes, came from McGinty, who curled into the sidenetting, whilst Kayara's long-range effort was also off target.
On the hour, the first clear chance of the night fell to the Blades. Kayara flicked over the home defence to give Porter space but the striker's shot was turned around a post by goalkeeper Caraux.
Morton hit back with three good chances in the space of 90 seconds, which the Blades contributed to with a number of stray passes. Firstly Saunders crowded out Wallace and then O'Brien's shot was tipped over the crossbar by Willis, whilst Wallace also went close with a half-volley.
However, on 69 minutes, the Blades grabbed the lead when another of Morton's triallists indisputably fouled Brandy just inside the box. PORTER took responsibility and calmly slotted home the spot-kick, sending the goalkeeper the wrong way.
Just a minute later Willis was forced into a save to maintain the advantage and as the tempo continued to improve, Saunders made the home goalkeeper tip another effort over.
The final ten minutes saw the Blades protect the lead by keeping possession with Collins making an important block and Willis showing a clean pair of hands to hold another shot before the final whistle signalled that Weir had kicked off his Blades reign with a victory.
The Scottish tour heads to Cowdenbeath on Saturday before a fixture at Raith Rovers next Wednesday.
Blades (first half): Howard, Westlake, Williams, Maguire, Hill, Doyle, McGinn, McFadzean, McDonald, Cresswell, Ironside.
Blades (second half): Willis, Saunders, Grainger, Collins, Higginbotham, Whitehouse, McGinty, Murphy, Brandy (McFadzean 82), Kayara, Porter.