Alonso, who once famously described his Honda power unit as a "GP2 engine", made the remark in the course of a fraught race that saw him finish 11th.
He received a five-second penalty after he made a mistake and crossed the pit entry, suffered a lengthy delay in the pits, and struggled for much of the race with a car that had an issue with a dislodged aero part.
Singapore was the first time in 2023 that Alonso, who was the team's only representative in the race after Lance Stroll's qualifying accident, had missed the points.
Krack understood why the Spaniard was so frustrated in the cockpit.
"As a team, we need to acknowledge if a driver is critical," he said when asked by Autosport about Alonso's comment.
"Obviously there is not the performance that he's expecting, and that he's used to, and then I think it's okay.
"We want them to give everything, and then it's normal that also sportsmen react like that. So it's not a problem."
Alonso had been on schedule for a solid sixth place in Singapore when his race began to fall apart.
"We thought we had a good rhythm," said Krack. "I think we knew upfront that it would be difficult to go with the front guys. So I think on the medium, everything ran pretty solid.
"Then after the safety car we fitted the hard tyres, and we struggled a bit more, we need to understand why. To a point where we said when the virtual safety car came we were not sure that we could go the full distance with a decent level of performance.
Source: Autosport