*Club domestic league appearances and goals, correct as of 27 April 2024 (UTC) ‡ National team caps and goals, correct as of 22:08, 17 November 2022 (UTC)
Dennis started the season on the bench mostly before being given his UEFA Europa League debut to Feyenoord on 3 November, which ended 1–1. After impressing against Feyenoord, he also played in the Ukrainian side's other group stage games, to Fenerbahçe and Manchester United. Zorya lost 2–0 in both matches and were eliminated from the group having finished in last place.
On 11 December, Dennis scored his second goal in a 2–0 win over Stal Kamianske. His performances attracted both Manchester City as well as an unknown Bundesliga side, who were interested in signing him in the winter transfer window.[5][6] However, Dennis instead ended up staying with Zorya for the rest of the season, helping them to a third place in the league with his six goals in 22 league appearances.
Club Brugge
Club Brugge announced on 30 May 2017 that they had signed Dennis on a four-year-deal for a fee of €1.2 million.[7] He was given the number 42 jersey shirt. Dennis started the season extremely well, scoring five goals in six matches, including one on his debut on 26 July 2017 to İstanbul Başakşehir, a 3–3 draw and a brace three days later in the league over Lokeren, which finished in a 4–0 victory.
On 25 January 2021, Bundesliga side 1. FC Köln announced that they had signed Dennis on a loan deal until the end of the season.[11] He made a total of nine league appearances during his time in Germany.
Watford
On 21 June 2021, Watford confirmed they had reached an agreement with Club Brugge for the transfer of Dennis.[12] A five-year contract was signed two days later.[13] On 14 August, Dennis scored on his Watford debut in their league opener against Aston Villa, where Watford won 3–2.[14] Dennis was nominated for the Premier League Player of the Month award for November 2021[15] after scoring and grabbing two assists in a 4–1 thrashing of Manchester United[16] and scoring in a 4–2 defeat at Leicester City.[17]
Nottingham Forest
On 13 August 2022, Dennis signed with Premier League side Nottingham Forest for an undisclosed transfer fee.[18] The transfer fee was reported to be £10 million.[19]
On 15 September 2023, Dennis signed with Turkish side Istanbul Basaksehir on loan for the 2023–24 season.[20] On 22 January 2024, Nottingham Forest terminated his loan deal with Istanbul Basaksehir to facilitate a move back to former club Watford on loan.[21]
International career
Dennis represented Nigeria at under-23 level[2] before being called up to the senior team. He made his debut on 10 September 2019 in a 2–2 friendly draw to Ukraine, coming on as a 82nd-minute substitute for Samuel Chukwueze.[22]
The Nigeria Football Federation attempted to call Dennis up to the squad for the 2021 Africa Cup of Nations however accused Watford of refusing to release Dennis and 'baring their fangs’, when, in fact NFF failed to ask for his release in time'.[23][24] Dennis was part of the Nigerian squad that lost on away goals with an aggregate score-line of 1–1 to the Black Stars of Ghana in the third round of the 2022 FIFA World Cup qualifying.[25][26]