Updated September 1, 2026. Arthur was announced by Santos on August 31, but the answer to “when can he play?” changes by tournament. In the Copa do Brasil, he cannot play the quarterfinal second leg against Palmeiras because the first leg of the tie had already been played. In the CONMEBOL Sudamericana, there is a regulatory path for Santos to register him for the quarterfinals, provided the club uses one of the permitted replacements and meets CONMEBOL's deadline. In the Brasileirão, Arthur is within the individual appearance limit from his previous club and can play after his BID registration and competition entry are completed, while Santos must also remain within its squad limits.
Quick answer: Arthur's status in each competition
| Competition | Can he play? | When and under what conditions |
|---|---|---|
| Copa do Brasil | Not against Palmeiras on Sept. 2 | The quarterfinal first leg has already been played. If Santos advances, Arthur can become eligible from the semifinal onward, provided he is in the BID, entered through the SNR before the semifinal first leg and the club has room under the limit for players who already represented another team in the competition. |
| CONMEBOL Sudamericana | He can be registered for the quarterfinals | The manual allows up to three replacements on the quarterfinal list. Form 6 must be submitted by 6 p.m. Paraguay time on Sept. 4. Registration remains subject to documentation and CONMEBOL approval. |
| Brasileirão | Yes, in principle | Arthur made 10 Série A appearances for Grêmio in 2026, below the maximum of 12 for an in-season switch between clubs. He can play from the day after his BID publication, once Santos enters him in the competition and provided the club-level limits are also available. |
Copa do Brasil: why Arthur cannot play the second leg against Palmeiras
The decisive point is not just the BID. The 2026 Copa do Brasil Specific Competition Regulations state in Article 6, paragraph 1, that in two-leg rounds a player's competition registration must be completed before the first leg of that round. If the first leg has already been played, the player can only become eligible in the next round if the club advances.
Santos lost the quarterfinal first leg 3-0 to Palmeiras on August 26, according to the official CBF match page. Arthur was not announced until August 31. Therefore, even if his name is published in the BID before the September 2 return match, the round-specific rule still prevents him from playing in that game.
If Santos advances, the situation changes. Article 5 sets the final registration deadline as the first business day before the first semifinal first leg, while Article 6 allows a player to compete from the day after his BID publication as long as all other requirements have been met.
There is another important detail: Arthur has already played in this Copa do Brasil for Grêmio. The official Grêmio vs. Confiança lineup from April 21 lists the midfielder in the fifth round. That does not, by itself, block a move. Article 7 allows a player to be registered by a second club if he played for his original club before the start of the sixth round, which Arthur did. However, each club may register no more than three players who had already appeared for another participant before the round of 16. Arthur is individually eligible under that rule, but Santos must also have room under the club-wide cap.
Sudamericana: playing for Grêmio in the group stage does not automatically block a switch
The Sudamericana works differently. The 2026 CONMEBOL Sudamericana Club Manual allows a player to be registered by up to two clubs in the same edition, with restrictions by stage. A player registered by one club in the group stage can be registered by another from the Round of 16 Playoffs onward; at the same time, a player cannot be registered in the Final Phase for more than one club.
Arthur did take the field for Grêmio in the group stage. CONMEBOL itself records his halftime entrance and an assist against Montevideo City Torque on May 26. Later, Grêmio announced that his contract would end on June 30, before the Final Phase began. That sequence is compatible with a new Santos registration for the quarterfinals; final confirmation, however, depends on the documents filed and CONMEBOL's validation.
For the quarterfinals, the manual provides for up to three list replacements through Form 6, with a deadline of 6 p.m. Paraguay time on Friday, September 4, 2026. That is the operational deadline that matters if Santos wants Arthur available against Atlético Mineiro.
The Santos roster page on CONMEBOL checked on September 1 did not yet list Arthur Melo. That is not the same as ineligibility: the quarterfinal replacement window was still open. The tie against Atlético Mineiro starts on September 9 at Vila Belmiro.
Brasileirão: the 12-match limit leaves Arthur eligible
In the Brasileirão, the main criterion for a player moving between Série A clubs during the season is the number of matches played for the original team. The 2026 Brasileirão Série A Specific Competition Regulations, in Article 12, allow a player to be registered by another club if he has appeared in no more than 12 matches for his previous club. An appearance means entering the field, either as a starter or substitute.
Arthur made 10 Brasileirão appearances for Grêmio in 2026. He is therefore below the individual cap of 12 and can switch clubs within Série A. The same regulations state that a player who has already represented one club may play for only one additional club in that edition.
That does not mean automatic clearance. Article 9 requires SNR competition registration and a BID record in favor of the new club. Article 10 says the player becomes eligible from the day after his BID publication, provided the other requirements have been met. In addition, each club may register up to five players who already appeared for other Série A clubs in 2026, with no more than three coming from the same original club.
On the night of August 31, Band reported that Santos was still waiting for Arthur's name to be published in the BID. Because the bulletin is updated by the CBF, that status can change quickly. A September 6 debut against Internacional has been reported as an expectation, but it only becomes possible if the registration and competition entry are completed in time.
What still has to happen before Arthur can take the field
- BID: Arthur's registration must be published in favor of Santos. In CBF competitions, match eligibility starts the day after publication as long as the other requirements have been met.
- Brasileirão: Santos must enter him in the competition through the SNR and remain within the roster limits and the cap on players arriving from other Série A clubs.
- Sudamericana: Santos must use one of the up to three quarterfinal replacements, submit Form 6 by 6 p.m. Paraguay time on September 4 and obtain CONMEBOL's documentary approval.
- Copa do Brasil: Arthur is out of the quarterfinal second leg. If Santos advances, his semifinal registration must be completed before the first match of that round, while the club must also respect the three-player cap for athletes who already represented another team in the competition.
The part that can change quickly
The rules above are stable within the 2026 regulations, but the documentary status is dynamic. BID records, good-standing lists and substitutions can be updated between this article's publication and the next match. The correct reading on September 1 is therefore: Copa do Brasil, not in the quarterfinals; Sudamericana, registration is possible and the deadline is still open; Brasileirão, eligible under the 12-match rule but still dependent on the registration steps required to play.
Sources consulted
- Santos FC — official Arthur signing announcement
- CBF — 2026 Copa do Brasil Specific Competition Regulations
- CBF — 2026 Brasileirão Série A Specific Competition Regulations
- CONMEBOL — 2026 Sudamericana Club Manual
- CONMEBOL — Santos roster and schedule in the 2026 Sudamericana
- Grêmio — statement on the end of Arthur's contract
