This was the first championship a girone unico (with only a group).
The division of the championship in two (federal and italian) wasn't formally cancelled. According to the article 2 of the Regolamento dei Campionati 1909-10 (Championship Rules):
According to La Stampa in an article dated December 24, 1909:
Foot-Ball, the official magazine of FIGC, in the classification considered US Milanese, Pro Vercelli, Ausonia and Doria as competing to "italian championship" since they were "pure italian teams"; the best placed among them at the end of the season would win the honorific title of "italian champions".
At the end of the season, there was a playoff between Inter and Pro Vercelli for the title of Federal Champion. The playoff was planned for April 24, but 3 players of Pro Vercelli had to play in a military tournament in that day. Pro Vercelli asked for the postponal of the match, but FIGC and Inter refused (since there weren't more other dates available because of the debut of the Italian National team, and because they thought the prorogation was a tactic to buy time to recover injured players). In order to protest, Pro Vercelli decided that the playoff would be played by Pro Vercelli Youth Team (players 11 years old). Result: Inter won easy the playoff 10-3, winning his first title. Pro Vercelli was accused of serious unsportsmanlike behavior by fans who saw the game.
The winner (and "Federal Champion") was Internazionale.
The "italian champion" (honorific title) was Pro Vercelli.
Source: Almanacco Illustrato del Calcio - La Storia 1898-2004, Panini Edizioni, Modena, September 2005 (Italian)
1 ^ The home team is listed in the left-hand column.
Colours: Blue = home team win; Yellow = draw; Red = away team win.
For coming matches, an a indicates there is an article about the match.
Internazionale
Goalkeepers
Defenders
Midfielders
Forwards