Aston Martin sprung a surprise at the start of 2023 by competing for podiums after finishing 2022 in a lowly seventh position in the F1 world constructors' standings.
A reinvigorated Fernando Alonso, who joined from Alpine, claimed six top-three finishes, although recently the Silverstone team has found the going got tougher.
Mercedes and Ferrari both took steps to rein Aston in, while McLaren too produced a remarkable car upgrade to put it firmly in the mix.
There are also questions on Aston's recent upgrades, with suggestions that the team has had to change its front wing amid an FIA flexi-wing clampdown.
The net result is that Aston has had to let Mercedes go in the fight for second and feels Ferrari breathing down its neck for third, the Scuderia now just five points adrift as the second half of the season gets under way this weekend in the Dutch dunes of Zandvoort.
While some of the early excitement on Aston's turnaround has petered out, Alonso still felt the team's first half of 2023 was "incredible".
But team principal Krack acknowledged the Lawrence Stroll-owned squad still has a lot of improvements to find to be considered in the same league as Mercedes and Ferrari, which both underperformed at the start of year.
"We have a long way to go, we have only made one step," Krack told Autosport in an exclusive interview. "And the progress will not be linear. You will have moments where you will overachieve, like we did in the beginning of this year.
"But you will also have moments where you underachieve, just purely because you are also affected by how other people are doing, which you have no control of.
Source: Autosport