Racing smash champions Clermont
Racing smash champions ClermontSHARE
Injury-ravaged Clermont, with 12 backs on the casualty list, slumped to a third successive league defeat which left them 10th in the table and seven points off the play-off places.
It also came just a week before they face Northampton in the European Champions Cup where, unlike their domestic form, they boast four wins in four games and are virtually assured of a place in the quarterfinals.
However, with that game in mind, Clermont rested their remaining fit backs Morgan Parra, Peter Betham and Nick Abendanon.
On the pitch on Sunday, they suffered two more injuries with Michael Simutoga and Ezeala, who was making his professional debut, both stretchered off.
Spanish teenager Ezeala was knocked unconscious after a second-half clash of heads in a tackle with Virimi Vakatawa.
"He is conscious, he is moving," said Clermont coach Franck Azema of the youngster who will be kept in hospital overnight for observation.
"We were really scared, all of us. When you put a kid, just 18, in there for his first game you don't want to see him have a night like that."
Racing moved into third place in the table, just a point behind leaders Montpellier.
They were already 14-0 ahead after just 10 minutes thanks to tries from Leone Nakarawa and Vakatawa.
Camille Chat, Dimitri Szarzewski, Teddy Thomas, Wenceslas Lauret, Henry Chavancy and a second for Vakatawa completed the rout with Racing racking up 38 unanswered points after the interval.
In Sunday's other match, Pau stayed on course for the play-offs after edging Toulouse 11-10.
Pau stay ninth in the table but just three points behind Toulon in fifth.
The teams scored a try apiece with Quentin Lespiaucq crossing for Pau who scored all their points in the first half.
Wandile Mjekevu grabbed Toulouse's try but they also had a try by Antoine Dupont ruled out for a forward pass by Gael Fickou.
"Our start was pathetic and I was a little worried," said Pau coach Simon Mannix who saw replacement forward Martin Puech red-carded after 70 minutes.
"But I am satisfied with the win and especially the last 10 minutes when we had 14 against 15. The defence was exceptional. We didn't allow them the position to get into penalty range. That's a sign of great character."
On Saturday, Montpellier gained a precious bonus point as they beat Stade Francais 28-16 to retake first place in the table from La Rochelle, who drew at last-place Oyonnax.
On a day of last-minute scores in the Top 14, Oyonnax twice struck late on to draw 38-38 with La Rochelle while Brive scored at the end to edge Toulon, 13-12.
In other matches, Bordeaux, in their first game under English coach Rory Teague, smothered Lyon 19-10 and Agen crushed third-place Castres 30-3.