But the Saints hooker was pitchside in Welford Road for Friday’s 29-15 win against Leicester – and Boyd issued a favorable post-match upgrade.
“Dylan has been to the specialist. It had been very positive,” he explained.
“I’m not certain when, but I’m really optimistic Dylan can play a few football before the close of the growing season.
“He might be just three to six weeks, however he is in a excellent space.”
Hartley is England’s second-most capped player, having played 97 internationals – 17 supporting recordholder Jason Leonard (114).
England’s next fixture is against the Barbarians at Twickenham on Sunday 2 June, the afternoon following the Premiership closing.
Following a summer break, Eddie Jones’ side are subsequently scheduled to play warm-up internationals – 2 against Wales, afterward home matches with Ireland and Italy – prior with their Rugby World Cup opener against Tonga in Sapporo on 22 September.