Goals from Danny Webber and Darius Henderson saw off the Irons in sweltering conditions with temperatures in North Lincolnshire believed to have been around the 30 degrees mark.
Big Sam said: "We have picked three difficult games on purpose. It has been hard work at Scunthorpe and we've seen things we need to sharpen up on. The lads are giving us things to consider."
Danny Webber who has bagged five goals in pre-season so far received some credit from his assistant manager. Ellis continued: "Webber is in a streak of form and all he can do is keep scoring goals, Henderson did well for the first game, he's not up to the fitness levels of our other lads but we will work on that in the next couple of weeks.
"We have 23 players fighting for places and we will have a better idea of the best eleven after the Huddersfield game next week."
The Blades continue embarking on their pre-season tour in the final two games next week. On Tuesday night It's off to Gigg Lane while on Saturday we travel to West Yorkshire to meet Huddersfield Town to round off pre-season with the next campaign only a week away.