It is the second straight time the Italian has qualified for an ATP 1000 quarter-final and he will face a stern test in second seed Alexander Zverev.
Prior to the year's first clay-court ATP Masters 1000 event, Alcaraz stated that he was not physically or mentally exhausted.
Returning to the Monte-Carlo Country Club this week, the defending champion expressed his confidence and excitement.
The competition is one of the oldest and most prestigious tennis tournaments in the world and 2022 will be the 125th year since its inception.
Thiem announced that he had tested negative for the virus and would undergo a medical examination before returning to action.
Apart from the four Grand Slams, the Monte Carlo Masters is arguably one of the most prestigious men's tennis competitions in the world today.
Rafael Nadal defeated Stefanos Tsitsipas 6-4, 6-7(6), 7-5 on Sunday to win the Barcelona Open for a record-extending 12th time.
King of Clay, Rafael Nadal, suffered a shock quarterfinal exit against Andrey Rublev at the Monte Carlo Masters last week.
Stefanos Tsitsipas was in the form of his life last week as he did not drop a set en route to winning the Monte Carlo Masters
The 22-year-old Greek player, Stefanos Tsitsipas, clinched the Monte Carlo Masters without dropping a set in the entire week