Panionios At the age of 11, Mavros joined the youth academy of the club and began his intensive involvement with football. The exclusion of his brother from the club's teenage section combined with the disappointment of his family brought him to train with the youth team of Olympiacos. There,
Elias Yfantis identified his potential and asked him to join the team. Panionios refused to give him his sport's card, preventing the transfer and Mavros became disillusioned and temporarily withdrew from the club's activities. The situation was resolved by the curator of the club Papidas, after a visit to his house and a promise to 14-year-old Thomas for participation in the youth team. There, he worked under
Dezső Bundzsák at the beginning and later
Joe Mallett who recognized and developed his talent, becoming the youngest player to have played in a
Greek championship match, at the age of 16, as well as the youngest scorer when on 17 January 1971, he scored the only goal in the 65th minute against Pierikos in a 1–0 victory. He also became an international at a very young age whilst not playing for any of the top clubs. On 16 September 1971, he made his European debut against
Atlético Madrid in the
first round of the
UEFA Cup. His appearance made him the then youngest player of a Greek football club to have ever played in a European competition. Initially Mavros played as a
left winger and later as a
striker, where he showed his scoring abilities, attracting the interest from major Greek clubs.
AEK Athens In the summer of 1975, the president of
AEK Athens,
Loukas Barlos was interested in signing Mavros, but the board of Panionios rejected all offers, refusing to sell their best player. AEK were about to relive the adventures of the transfer of
Kostas Nestoridis in 1955. The desire of Mavros to play for the AEK of the time, as well as his appreciation for Barlos were enough to overcome the efforts of the president of Panionios, Tsolakakis to block the transfer. It was later revealed that, when Mavros signed his contract with Panionios, he was still a minor, thus rendering the contract invalid. Panionios still blocked the transfer, which led to a legal dispute between the two sides that lasted for an entire season. During this period, he was unable to compete in an official match for either side and thus he was limited to playing in only friendly games with AEK. On 2 July 1976 the dispute was eventually settled out-of-court and Mavros was transferred to AEK Athens for the amount of 10 million
drachmas. The resolution of the case brought satisfaction to both Barlos and Mavros who developed a "father-son" relationship. From his first season, he became an integral part of the team, helping them reach the
semi-finals of the UEFA Cup. With the arrival of
Dušan Bajević he formed one of the club's most prolific attacking duos. The following season, he had a starring role in AEK winning the domestic double, emerging as the
top scorer of the league with 22 goals. The team of Barlos did not stop there and won a second consecutive championship in 1979, while they missed the chance to win the domestic double, losing the
Cup to Panionios in the final. Mavros was again the league's top scorer making a career record of 31 goals, while his performances of that season won him a
Silver Shoe, finishing 3 goals behind
Kees Kist of
AZ. The era after the departure of Barlos was marked with administrative and financial instability within the club, while the signings did not meet expectations, as the team became progressively weaker. In that period of decline for the club, Mavros stayed and with his leading presence helped maintain the team's competitiveness. He was particularly popular among the supporters of AEK, partly due to his loyalty to the club during a period of decline and his scoring performances in matches against Olympiacos. He earned the nickname "The God"
(), while the lexicographer Faidon Konstantoudakis also coined the nickname
"Theomas" () (paraphrase of his first name to resemble the Greek word for God) and whenever he scored the whole stadium chanted
"Who, who, who? Mavros the God" (). On 18 August 1981, Mavros was called to
Europe XI to play against
Czechoslovakia for the 80th anniversary of the
Czechoslovak Football Association. In 1982, he played a key role in eliminating Olympiacos in the
quarter-finals of the Cup with 2 wins and his goal in the victory by 0–1 in the second leg at
Karaiskakis Stadium. In the counterattack of AEK that led to the goal, Mavros got the ball at the center of the field and dribbled into the penalty area and many supporters of the red whites began leaving the stadium confident of the upcoming goal of Mavros and the consequent elimination of their team. In the
final against
PAOK at
Olympic Stadium, his goal and another by
Vangelis Vlachos led the club to win a title after 4 years. In the following season he renewed his contract with the club receiving 45 million drachmas from the then president, Lefteris Panagidis. On 22 June 1984, Mavros was called to the
World XI alongside his countryman
Vasilis Hatzipanagis and other players such as
Franz Beckenbauer,
Ruud Krol,
Johan Neeskens,
Peter Shilton,
Kevin Keegan,
Mario Kempes,
Hugo Sánchez and
Felix Magath. Approximately 20,000 Greek spectators were present at
Giants Stadium to watch World XI playing against
New York Cosmos in a 3–1 win. In fact, according to Mavros, in the game, Beckenbauer told him "At last, you came.", referring to the constant interest of his team,
New York Cosmos for Mavros. On 27 January 1985, Mavros also became one of the nine
Greek players in history to have scored 5 goals in a match against
Egaleo where AEK won by 5–2. At the end of the season he finished as the league’s leading scorer for the third time in his career with 27 goals. In 1987, the manager of the club,
Nikos Alefantos asked the president,
Andreas Zafiropoulos not to renew the contract of Mavros, as he thought the player was "too old" to play for a club of that level. This was confirmed on 11 April 1987, in the home match against
Apollon Kalamarias, when at the 80th minute Alefantos substituted Mavros, being booed by the fans. Zafiropoulos agreed to the request of the manager and Mavros was released from the club and returned to his former club, Panionios. During his spell at AEK he won 2 championships and 2 Cups, including the domestic double of 1978.
Return to Panionios Mavros proved the former manager and the administration of AEK Athens wrong in his return to Nea Smyrni. With Panionios, in 1990 he finished as top scorer in the league with 22 goals, at the age of 36, becoming the oldest player in Greece to win the award. Upon his return to
Nea Filadelfeia on 28 October 1989, as an opponent of AEK, Mavros equalized the match at the 27th minute and didn't celebrate, with the crowd chanting his name as if he had just scored for AEK, showing their love and appreciation to his face, who responded by applauding them back and sending them kisses, wiping away a tear of joy. Before retiring in 1991, Mavros managed to score a total of 51 goals in 89 matches on his second spell at the club and surpassed his former teammate at AEK Athens,
Mimis Papaioannou as the all-time top scorer in the Greek championship. ==International career==