2018: World Cup
"The squad is the worst in their history. Even having the best player in the world was not capable of creating a competitive team. All the decline of recent times was hidden by this unrivalled genius [Messi]"
– Former Argentine player Osvaldo Ardiles on the decline in quality of Argentina being masked by Messi.
Following on from their poor qualification campaign, salvaged by Messi, expectations were not high going into the 2018 World Cup, with the team, without an injured Messi, losing 6–1 to Spain in March 2018. Prior to Argentina's opener, there was speculation in the media over whether this would be Messi's final World Cup. In the team's opening group match against Iceland on 16 June, Messi missed a potential match-winning penalty in an eventual 1–1 draw. In Argentina's second game of the 2018 World Cup on 21 June, the team lost 3–0 to Croatia. Post match the Argentina coach Jorge Sampaoli spoke of the lack of quality in the team surrounding Messi, "the reality of the Argentina squad clouds his [Messi's] brilliance". Messi had just 49 touches of the ball and only two inside the Croatia penalty area. Sampaoli stated, "we quite simply couldn't pass to him to help him generate the situations he is used to. We worked to give him the ball but the opponent also worked hard to prevent him from getting the ball. We lost that battle." Croatia midfielder Luka Modrić also stated post match, "Messi is an incredible player but he can't do everything alone."
Messi celebrating a goal against Nigeria at the 2018 FIFA World Cup
In Argentina's final group match against Nigeria at the Krestovsky Stadium, Saint Petersburg on 26 June, Messi scored the opening goal in an eventual 2–1 victory, becoming the third Argentine after Diego Maradona and Gabriel Batistuta to score in three different World Cups; he also became the first player to score in the World Cup in his teens, twenties, and his thirties. A goal of the tournament contender, Messi received a long pass from midfield and controlled the ball on the run with two touches before striking it across goal into the net with his weaker right foot. Argentina progressed to the second round as group runners-up behind Croatia. In the round of 16 match against eventual champions France on 30 June, Messi set up Gabriel Mercado's and Sergio Agüero's goals in a 4–3 defeat, which saw Argentina eliminated from the World Cup. With his two assists in his team's second round fixture, Messi became the first player to provide an assist in the last four World Cups, and also became the first player to provide two assists in a match for Argentina since Diego Maradona had managed the same feat against South Korea in 1986.
Following the tournament, Messi stated that he would not participate in Argentina's friendlies against Guatemala and Colombia in September 2018, and commented that it would be unlikely that he would represent his nation for the remainder of the calendar year. Messi's absence from the national team and his continued failure to win a title with Argentina prompted speculation in the media that Messi might retire from international football once again. In March 2019, however, he was called up to the Argentina squad once again for the team's friendlies against Venezuela and Morocco later that month. He made his international return on 22 March, in a 3–1 friendly defeat to Venezuela, in Madrid.
2019: Copa América third-place
On 21 May 2019, Messi was included in Lionel Scaloni's final 23-man Argentina squad for the 2019 Copa América. In Argentina's second group match of the tournament on 19 June, Messi scored the equalising goal from the penalty spot in a 1–1 draw against Paraguay. After coming under criticism in the media over his performance following Argentina's 2–0 victory over Venezuela in the quarter-finals at the Maracanã Stadium on 28 June, Messi commented that it had not been his best Copa América, while also criticising the poor quality of the pitches. Following Argentina's 2–0 defeat to hosts Brazil in the semi-finals on 2 July, Messi was critical of the refereeing during the match. In the third-place match against Chile on 6 July, Messi set-up Agüero's opening goal from a free kick in an eventual 2–1 win, to help Argentina capture the bronze medal; however, he was sent off along with Gary Medel in the 37th minute of play, after being involved in an altercation with the Chilean. Following the match, Messi refused to collect his medal, and implied in a post-match interview that his comments following the semi-final led to his sending off. Messi later issued an apology for his comments, but was fined $1,500 and was handed a one-match ban by CONMEBOL, which ruled him out of Argentina's next World Cup qualifier. On 2 August, Messi was banned for three months from international football and was fined $50,000 by CONMEBOL for his comments against the referee's decisions; this ban meant he would miss Argentina's friendly matches against Chile, Mexico and Germany in September and October.