Kalamafoni, on the advice of a neurologist, has been stood down for three months after reporting with concussion symptoms following the away defeat at Saracens.
Scans have revealed that May, who was replaced in England’s Six Nations victory over Wales at Twickenham in around 4 of the 2020 Championship, suffered a fractured cheekbone.
The Tigers back has had surgery and is expected to be side-lined for an extended period.
“As we enter the final half of the Premiership season and approach the knockout stages of Europe, the loss of three players is a blow"Geordan Murphy
Meanwhile, scans have revealed that McPhillips, who was helped from the field early in his Premiership starting debut away to Saracens, has suffered a posterior cruciate ligament (PCL) tear in his right knee.
He is expected to be unavailable for three months.
Speaking about the loss of the trio, Tigers head coach Geordan Murphy said: “First and foremost, we are all very disappointed for the three lads.”
“As we enter the final half of the Premiership season and approach the knockout stages of Europe, the loss of three players is a blow.
“All three are ultimate professionals and I’m confident they will commit fully to their rehab in a bid to return to action this season.”
The loss of the trio follows a suspension handed down to Freddie Steward (England Rugby U20s) for an infringements in Round 4 of this season’s Under-20s Six Nations.
“We are fortunate to have returning players from the Six Nations to add vital depth to the squad,” said Murphy.
Fellow forwards Tomás Lavanini and Hanro Liebenberg, who were left out of the Round 13 fixture, will also be considered for the trip south to take on Exeter Chiefs.
“We are hopeful of seeing Jordan [Taufua] and Noel [Reid] back in contention for the trip to Sandy Park,” Murphy added.
“Tomás and Hanro have been playing for the better part of twelve months, after finishing up in the Southern Hemisphere before joining us, and we made the call to give them a break for two weekends moving into the next block of fixtures.”
Tigers take on Exeter Chiefs in Round 14 on Saturday, March 21, before welcoming Bath Rugby to Welford Road on Friday, March 27 in the first of three successive home fixtures, including a European quarter-final against Castres and a Good Friday showdown with London Irish on April 10.