Barca, who are third and 11 points behind the leaders, face Alaves at home later on Saturday before Real Madrid host Valencia on Sunday.
Machín takes over following a season in which the Basque Country club finished 16th in the first division of the Spanish league, three points above the relegation zone.
LaLiga club logos explained: What does the tree on Athletic Bilbao's escudo mean? Is there an English reference to Barcelona's logo?
Coronavirus pandemic: LaLiga side Deportivo Alaves confirm 15 positive COVID-19 cases at club, including three first-team players
There have been 15 positive cases, three of which are from the Deportivo Alaves first-team squad and seven members of the coaching team, said a statement issued by the club
LaLiga: Lionel Messi, Luis Suarez and Antoine Griezmann find the target as Barcelona end year top of the league
Lionel Messi closed the year with a total of 50 goals for club and country for the sixth straight time, helping Barcelona stay top of the league entering the holiday break.
LaLiga: Real Madrid battle past Alaves to top league standings with hard-fought victory; Real Sociedad clinch thumping win
Sergio Ramos and Dani Carvajal scored second-half goals as Real Madrid beat its tough Basque Country opponent 2-1 to take the league lead from Barcelona, who visit fifth-placed Atlético Madrid on Sunday.
LaLiga: Portu brace guides Real Sociedad to 2-1 win at Granada to pull level with Barcelona, Real Madrid
Real Sociedad's fourth victory in seven away matches moved them into third place, behind the league's two traditional powerhouses on goal difference.
Athletic Bilbao is in 18th place of the 20-team league and level on points with Villarreal, which is the last team in safety.
LaLiga: Deportivo Alaves miss out on opportunity to climb atop standings after defeat to struggling Leganes
Deportivo Alaves could have leapfrogged Barcelona, Sevilla and Atletico Madrid with victory, but instead remain fourth in the Spanish top flight, three points clear of sixth-placed Real Madrid.
LaLiga: Tiny Deportivo Alaves climb atop Spanish league standings with gritty victory over Celta Vigo
Alaves have 17 points from nine games with Sevilla on 16 and Barcelona on 15 before they face each other on Saturday.
LaLiga: From near bankruptcy to third in standings, the story of Deportivo Alaves, who stunned Real Madrid
Almost 10 years ago, Deportivo Alaves, a tiny club from Vitoria-Gasteiz, were staring at bankruptcy. On Saturday, they ascended to third in LaLiga after stunning Real Madrid.
LIonel Messi opened the scoring and helped set up goals from Neymar and Paco Alcacer just before half-time as Alaves slumped to defeat in their first Spanish Cup final.
Lionel Messi and Barcelona gave coach Luis Enrique a victorious send-off as the Catalans retained the Copa del Rey with a 3-1 win over Alaves on Saturday.
Barcelona coach Luis Enrique expects his team to adapt to Lionel Messi's absence in the same manner as last season when they won eight of their 10 games without the talismanic forward.