The Fir Park side had to desperately defend the lead John Sutton's 20th minute goal gave them during the final 20 minutes, but had they converted one of the numerous chances they had while on top the game could have been killed off considerably earlier.
"I was delighted with the win especially the first half as we stopped them playing," he said.
"We knew a second goal would kill them off and their keeper has had a couple of terrific saves. However, while it is only 1-0 it gives the other team belief. And give credit to Thistle who made a right good go of it in the final 20 minutes."
The Well boss admitted to having a few anxious moments towards the end but was grateful for the clean sheet.
"After losing five goals in our last two games, it was pleasing to keep a clean sheet," he added. "That gives us a platform to build on and we have now won 50% of our games and with 1-0 wins."
It was a first goal of the season for Sutton, who was delighted to open his account.
"It is great to get the monkey off your back and get your first goal of the season," he said. "I scored 17 goals in my first spell at Motherwell and it gives me something to aim for. I also think I can create a good partnership with Henri Anier as we have only started once together."
The two looked strong together, and only a superb one-handed save from Scott Fox denied Anier his third goal of the season.
But it was Thistle who finished on top, albeit unable to truly test Motherwell goalkeeper Lee Hollis.
That left Alan Archibald reflecting on a disappointing end to his side's unbeaten run.
"It is not nice to taste defeat for the first time and it is a sore one to take but we didn't turn up in the first half," the Thistle boss said.
"Although we were better in the second 'Well had a game plan and pressed us in the first half. We played the game at our tempo in the second and attacked their goal and maybe did enough for a point but they might have been picked us off with a second on the counter."
Thistle will not have to wait long for an opportunity to bounce back.
Looking ahead to Tuesday's League Cup tie with Cowdenbeath Archibald was keen to emphasise the importance of the game.
"The players were in on Sunday preparing for Tuesday and getting treatment for a couple of knocks. We have a poor record in the League Cup and we will be preparing for Tuesday's tie as if it was Premiership game."
With Motherwell not involved until the next round McCall will spend the free week looking to add to his squad.
"I am hopeful of getting one more player in," he said. "We need a bit of pace and someone who can bring a bit of variety."