The Netherlands have not won the European Championship since 1988 – when current boss Koeman was a player for them – but are among the favourites to triumph in Germany.
They possess a strong blend of youth and experience, despite losing key playmaker Frenkie de Jong just before the tournament with an ankle injury, and had been in strong form going into these Euros with back-to-back 4-0 friendly wins against Canada and Iceland.
Their confident and accurate passing led to a number of chances and they should have been out of sight, before Buksa struck with one of Poland’s first chances.
Gakpo deservedly got them level but finishing continued to be an issue for the Dutch as opportunities to take the lead came and went.
Koeman sent on one-time Manchester United loanee Weghorst as a late throw of the dice and it quickly paid off as the big striker showed the movement and finishing his side had lacked to secure three valuable points.
This was more late heroics from Weghorst, who scored a stoppage-time equaliser against Argentina at the 2022 World Cup in Qatar.
"Wout Weghorst was able to play and he has added value to the team. He has a different way of behaving and that is what we needed," Koeman said.
"This should have been 4-1 in favour of us after one hour. We played very well but couldn't finish opportunities.
"Cody Gakpo also played very well. He was dangerous and we should give him the ball more often."