Norris stayed away from the track on Thursday after experiencing a bout of food poisoning, and the team had Nyck de Vries waiting on standby.
However, Norris was able to drive on Friday, and took an encouraging fourth place in qualifying.
In Saturday’s sprint, he slipped back to seventh, but he achieved the team’s target of losing out only to the cars of the top three teams while also overtaking poleman Kevin Magnussen.
After the contest, Norris admitted that he didn’t feel well again, and he was excused from media and other duties to help ensure he will be fit enough to take part in Sunday’s main race.
Seidl said there was no sign that Norris’s performance was compromised in the sprint.
“I'm confident, after a good rest again overnight, that he will be fine tomorrow,” he said when asked by Autosport about Norris’s condition.
“I think, if you look back at what he pulled off and how he was tackling the race today, how he was managing also the tyres to make sure he was there when he needed to be to make the move on Kevin, which was the goal for today, it didn't seem that there was anything missing.”
Norris scored two valuable points for McLaren on a day when Alpine, the team’s rival for fourth place in the constructors' championship, suffered badly after Fernando Alonso and Esteban Ocon collided.
Daniel Ricciardo benefited from the clash, moving up from 14th to take 11th on the grid for Sunday’s main event.
“Obviously we’re pretty happy after the sprint today because in the end the objectives we had for the day were to finish as best of the cars behind the top three teams,” said Seidl.
“Because we need to acknowledge that, when the six cars of the top three teams are doing the job they should do, then they're out of reach for us.
“So very happy with scoring P7 with Lando, obviously a good starting position for tomorrow to score good points.
“The second objective was to move forward with Daniel, to get him in a better position after a difficult qualifying for fighting for points tomorrow. Both objectives achieved, and therefore very happy with today's outcome.
“And then of course with the incidents on Alpine's side it put us even in a better position for tomorrow to score good points in the constructors’ championship against our main competitor.”
However, Seidl cautioned that Alpine could still be a threat, despite Ocon and Alonso starting Sunday’s race from 17th and 18th respectively.
“I think we've seen several times this year that you can never feel safe because Alpine have shown that they have very good race pace,” Seidl added.
“At the same time, everything we have seen so far from our car this weekend [means] we should be in a good shape as well tomorrow.
“But with the weather forecast that is around anything can happen so we will tackle the challenge tomorrow as we always do, which is focus on ourselves.
“We’ll make sure we execute a clean race and then hopefully we score more points than Alpine in order to keep the battle alive for P4.”
