Toro Rosso and Honda added expectation "that should not have been there" early in its Formula 1 partnership when it finished fourth in Bahrain, Brendon Hartley believes.
Pierre Gasly gave Honda its best result since it returned to F1 in 2015 when he finished fourth in the second race of the season.
The team has scored points in two of the other five races, Hartley with a 10th-place finish in a chaotic Azerbaijan GP and Gasly with seventh last week in Monaco.
Toro Rosso has not been a consistent performer in F1's midfield and Hartley explained that Bahrain produced "a perfect storm" for it and Honda to excel, which wrongly raised external expectations.
"It's very fair to say that we over exceeded all of our expectations in Bahrain," Hartley told Autosport.
"Our brief before the start of the season was, 'Look guys, the first few races are going to be really tough for us'.
"We spent all of this time and energy incorporating Honda and there has been a lot of changes behind the scenes in aerodynamics, we've probably taken one step back to take two step forwards later in the season.
"[Then we go] to Bahrain and blew all of our expectations out of the water, and probably for everyone else as well they would have expected that again."
The Bahrain race was followed one week later by the Chinese GP, in which Toro Rosso struggled significantly.
Although Hartley scored his first point in F1 in Azerbaijan that was another tricky race, and the team has adapted its analysis to understand why Bahrain was so strong rather than why the following races were so tough.
"We seem to be very light on tyres and I think in Bahrain we got them in the perfect window, others didn't," said Hartley.
"We're poor on aero sensitivity and there was no wind.
"Since then we haven't had the pace in the race. There is light at the end of the tunnel, an update on the floor [introduced in Monaco] and an engine upgrade coming for Montreal.
"Everyone's motivated, working hard, but I think in some ways that result in Bahrain added all this expectation that maybe shouldn't have been there.
"But that's Formula 1 and you see other teams struggling from one week to the other as well."
Honda technical director Toyoharu Tanabe told Autosport that they had "no idea of our competitiveness" pre-season because of the new partnership.
He admitted: "In Bahrain the result was much higher than our expectations.
"We need to calm down and keep working, step by step, to improve our performance.
"We know we are now behind and we are trying to catch up."