But an instant replay from another angle shows the referee told him to re-enter just before the ill-fated back pass was played.
A late goal from Krychowiak went some way to make up for his mistake but it was too little too late as Poland fell to defeat.
Senegal is tied for the group lead with Japan, which upset Colombia 2-1 earlier.
Despite putting in a limp and leaden performance himself, Lewandowski seemed to point the finger at his teammates for their errors, which ultimately cost Poland the game.
The African side – which shocked France on its World Cup debut in 2002, its only previous appearance – gradually started to dominate but the opening goal had a large slice of good fortune. This team was fast, this team was physical and in Aliou Cisse they had a coach who understands African football and what the World Cup means to Senegal more than anyone else.
‘I was the only one who saw the danger so I had to react or otherwise the player was through on goal, but he got in front of me. Poland returned for the first time since 2006.
Sadio Mane & Robert Lewandowski start for their respective sides and in a unusual, (not really) quirk of fate are both captains for their countries! The inclusion of all four attackers was perhaps recognition of the fact Senegal often struggle for midfield creativity, and it paid off with a huge opening-game victory.
Robert Lewandowski is the latest star player to struggle at the tournament without the support of his high-quality club teammates.
Subs: Fabianski, Jedrzejczyk, Bednarek, Goralski, Linetty, Teodorczyk, Glik, Peszko, Bereszynski, Kurzawa, Kownacki, Bialkowski.
Senegal: Khadim N’Diaye, Wague, Sane, Koulibaly, Sabaly, Sarr, Alfred N’Diaye, Gueye, Niang, Mane, Diouf.
Krychowiak put Poland in trouble with a woeful bouncing back pass, but Szczesny opted rashly to charge out of his penalty area. But from a decent position, the Senegal forward drags his shot well, well wide.
But the mood reportedly turned sour after Poland scored its goal in the 2-1 loss.
Senegal’s players celebrate their win over Poland. What is Krychowiak doing?! The goalkeeper doesn’t know whether to come or not, he eventually decides to but doesn’t reach it and Niang races in and taps it into an empty net.
The taller Lewandowski operated more as a traditional target man, trying to create options for Poland in the box when they were on attack. Krychowiak pulled a goal back, but it was not enough for Poland.