The Force, in their first season in the top flight, trailed 57-46 in the fourth quarter but went on a 14-3 run – capped by McCann’s three – to seal the match.
Sharks were still without point guard BJ Holmes, but entered the game in good form after back-to-back victories over the Christmas period.
Former Junior Sharks player Will Hall made an impression in the first quarter as his six straight points enabled Leeds to take an early 12-8 lead.
However, Sharks point guard Nick Lewis scored five in a 7-0 close to the period and Zach Gachette added a two to open the second quarter and Sheffield led 17-12.
New Force signing Sam Attah single-handedly kept his team in the contest before half time.
The recruit from Durham Wildcats scored 14 of Leeds’s 19 points as the first half ended tied at 31-31.
An Attah two-pointer briefly put Leeds ahead at the start of the third quarter before a 5-0 Sharks run made it 36-33.
Sheffield could get no further clear than 45-40 as Force pegged their hosts back to 48-46 heading into the final quarter.
Before the game, Force head coach Matt Newby was delighted with the arrival of Attah, the 6ft 4ins forward, who avraged 12.9 points and 3.3 rebounds in 10 games for the Wildcats, a team Leeds have beaten twice in the BBL Championship.
“In Sam we have found a player who is level-headed, committed and one that offers consistent output across minutes played,” said Newby.
“He rebounds well and is proven in terms of consistent scoring. We see Sam as a strong addition to our line-up.”