Siasia, 50, managed the Super Eagles over two separate spells and was eager to give his opinion on the Rohr's latest 30-man squad announcement ahead of the global event in Russia next month.
With the African giants drawn with Argentina, Croatia and Iceland, the German went for a squad with a European core, while seven players will still be cut before the 4 June deadline set by FIFA.
However, Sissia claims Al Ahly forward Junior Ajayi deserved a look in due to his exploits with the Egyptian giants this season, as he scored 10 goals and registered 11 assists in 32 games across all competitions from a left-wing role.
"Junior [Ajayi] has proven himself with the Olympic team and he is doing well in his club in Egypt. I think he should be given at least a chance to be part of that 30 man list," Siasia told Nigerian outlet TheCable.
"Ajayi came in for just about one minute. He trained with them, that's not the same. Training and playing is not the same thing. If you look at Victor Moses in training, you won’t play him.
"I am telling you the truth. I am not saying that's the same thing Ajayi did but they have to give him a chance."
Provisional 30-man squad:
GOALKEEPERS: Ikechukwu Ezenwa (Enyimba), Daniel Akpeyi (Chippa United), Francis Uzoho (Deportivo de La Coruna), Dele Ajiboye (Plateau United)
DEFENDERS: William Troost-Ekong (Bursaspor), Leon Balogun (Mainz 05), Ola Aina (Chelsea), Kenneth Omeruo (Kasimpasa), Brian Idowu (Amkar Perm), Chidozie Awaziem (Nantes), Abdullahi Shehu (Bursaspor), Elderson Echiejile (Cercle Brugge), Tyronne Ebuehi (ADO Den Haag), Stephen Eze (Lokomotiv Plovdiv)
MIDFIELDERS: John Obi Mikel (Tianjin Teda), Ogenyi Onazi (Trabzonspor), John Ogu (Hapoel Beer Sheva), Wilfred Ndidi (Leicester City), Uche Agbo (Standard Liege), Oghenekaro Etebo (Las Palmas), Joel Obi (Torino), Mikel Agu (Bursaspor)
FORWARDS: Odion Ighalo (Changchun Yatai), Ahmed Musa (CSKA Moscow), Victor Moses (Chelsea), Alex Iwobi (Arsenal), Kelechi Iheanacho (Leicester City), Moses Simon (Gent), Junior Lokosa (Kano Pillars), Simeon Nwankwo (Crotone)