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.
"And we decided to change, and then the sequence of events, the penalty, the pitstop went wrong, and then we came out in a really bad position. And that was it at the end."
Alonso had looked strong on long runs in Friday practice in Singapore, and Krack admitted that the team needed to review what went wrong over the course of the weekend.
"We need to really understand what happened," he said. "We also have a little bit of damage on the car that we need to understand, how much it did.
"We had an issue on one of the suspension fairings, an aero part. We saw it on the pitstop, and we saw it in the pictures.
"We had three different specs of tyres. And Singapore is also somewhere where you run close in traffic all the time, which is affecting always a lot and you don't know how much are others saving, how much are people managing? So this is one of the most difficult races always to understand."
Krack downplayed Alonso's pit entry mishap, which triggered the penalty.
"We need to review that," he said. "Because there are some settings to be made, if they were made, and if he was also reminded to do them. So I will be careful about [calling it a] mistake until we have analysed that."
