Aston Martin team principal Mike Krack has criticised the "borderline" driving antics of Alfa Romeo's drivers at the season-ending Abu Dhabi Grand Prix.
The two teams were separated by only five points ahead of the Yas Marina event in the race for sixth in the constructors' standings.
Both Lance Stroll and Sebastian Vettel finished in the points with Alfa Romeo failing to score, meaning that Aston Martin drew level.
But Valtteri Bottas' fifth-place finish at the Emilia Romagna Grand Prix meant the Swiss-based team took sixth in the championship on countback.
Stroll and Vettel were forced to pass both Bottas and Zhou Guanyu on track as strategy played out, with Krack left unimpressed by the defensive manoeuvers displayed.
Asked if it was frustrating that the team missed out on championship position, Krack replied: "Not frustrating, we shouldn't be frustrated.
"[It has been] a great end of the season overall, and it could also have balanced in the other direction.
"So frustration now would not be appropriate.
"Alfa focused completely on us. Some of the manoeuvres were a bit borderline.
"But we were anticipating this could happen. We were upfront, be a bit conservative when we pass them and both drivers handled it very well."
Alfa Romeo had no bearing on Vettel strategy
Vettel was left frustrated by a one-stop strategy that saw him drop down the order during the race, with the retiring German believing Aston Martin threw away sixth in the standings.
But on whether there was an eye on out-guessing Alfa Romeo's strategy when selecting its own tactics, Krack explained: "We didn't want to look at Alfa in this case. It was a close call between one and two [stop strategy].
"Some people did one, some did two.
"At the end of the day we tried to maximise the chances and we did not look at Alfa Romeo.
"I understand Sebastian was frustrated because he saw his team-mate coming on a different strategy.
"But this is something that in a race you have to decide. It's fine."