Helped by problems for Max Verstappen and a red flag that curtailed track action, Alonso qualified second behind Sergio Perez in Florida, matching his previous best performance of the year in Jeddah.
Asked about the prospects for a victory, Alonso was keen to downplay his chances.
"I don't think that we have to target a win, especially after how the weekend went," he said.
"I think even the podium is going to be difficult, but we do our race. We've been doing this the whole season, we are in a privileged position, we never expected to be here.
"So, every lap we do, every race lap that we will do in this kind of position is a gift at the moment. So, I think the team is enjoying it.
"We will try to pass Checo into Turn 1, because we love to lead the race, at least for a few laps. And after that, we will end up in the position we deserve.
"If it's P5, it's going to be P5. If it's P7, P7. If it's another podium it will be fantastic. But I think it's going to be a tough race."
However, Krack said that Aston has to target victory given Alonso's front-row starting position.
"The opportunity is there," he said when asked by Motorsport.com about his driver's chances.
"I mean, if you start from the first row, I said it also in Jeddah, if you start from the first row, your aim has to be to win the race.
"But, again, we have strong competitors that didn't get it all together [in qualifying] except Sergio. But we'll try. We'll give it our best."
Krack admitted that it's been hard for the team to get a proper understanding of the Miami track given the changing conditions.
"It was not an easy one [on Friday], the first session," he said. "With a huge track improvement it was very, very difficult to read the track.
"You do your simulations, and we had Baku also resurfaced not long ago, so we thought it would be probably similar to that. And it wasn't.
"And this puts you a bit on the back foot. Then we had two red flags, then you go out, and you don't know really where you are.
"And I think this we carried this not being 100% sure where we were into all the sessions up until qualifying."
Krack said that lack of information also impacts the race.
"At the moment, we really have no real knowledge about the track, because of the red flags," he said.
"Nobody did any long runs [on Friday]. So it will be one where you have to make these calls in the race, which makes it quite interesting."
However, he did acknowledge that Aston's good tyre degradation could be an advantage on Sunday relative to rivals.
"We cannot deny that we have been having a strong race car in all the previous events," he said. "So it's a strength that we can rely on. But still you have to do it.
"The race is long, and maybe others have improved their cars. So it is not a given that we will just have a strong race."
Krack also admitted that the team had made a mistake by not giving Lance Stroll a second set of new tyres in Q1 and hoping that the Canadian could emulate Alonso and get through with one set, which he didn't manage to do.
"There was no need to take that risk," he said. "And I think as a team, have some stats, some predictions, to get yourself what the cut-off will be.
"And in this thing, we were not good enough. I think we were maybe a bit greedy, trying to move forward and carry it into Q3 to have another set, on additional set. But we have to take our lesson from it and do better next time."
