The Prophet 'Isa (as) will follow the Mahdi and the Mahdi will serve as imam in the prayer (salat) to the Prophet' Isa (as)

Naim Abu Said narrated that the Messenger of Allah (saas) said:
Isa 'Ibn Maryam, will descend, and recite the daily prayer behind
Mahdi. (Al-Burhan fi `Alamat al-Mahdi, p. 78)
In Musannaf of Ibn Abi Shayba, Ibn Shirin narrated. He said:
The Mahdi is one of this community and will serve as imam to the
Prophet 'Isa (as). (Jalaladdin as-Suyuti, Al-Burhan fi Alamat
al-Mahdi Akhir al-Zaman, Al-Muttaqi al-Hindi, p. 79)
Naim ibn Hammad narrated from Abdullah ibn Amr. He said:
The Mahdi is the one whom 'Isa ibn Maryam (as) will perform the
daily prayer behind. (Jalaladdin as-Suyuti, Al-Burhan fi Alamat
al-Mahdi Akhir al-Zaman, Al-Muttaqi al-Hindi, p. 79)
It is narrated on the authority of Abu Huraira that the Messenger of
Allah (saas) observed: "What will be your state when the son of
Maryam descends amongst you and there is an Imam amongst you?"
(Sahih Muslim, Book 001, Number 0290)
Jabir ibn 'Abdullah reported: "I heard the Messenger of Allah (saas)
say: 'One section of my people will not cease fighting for the Truth
and will prevail till the Day of Resurrection. 'Isa son of Maryam
will then descend, and their (the Muslims') commander will invite
him to come and lead them in prayer, but he will say: No, some
amongst you are commanders over others (amongst you). This is an
honor from Allah for this Ummah.'" (Sahih Muslim, Book 001, Number
0293)
While their Imam is going forward to lead the people in the Salat
al-Subh (the morning prayer), 'Isa son of Maryam will descend. The
Imam will step back, to let 'Isa lead the people in prayer, but 'Isa
will place his hand between the man's shoulders and say, "Go
forward and lead the prayer, for the Iqamah was made for you." So
the Imam will lead the people in prayer… (Ibn Majah, Kitab al-Fitan,
Tradition No. 4077, 2: 1363)