Simmons left the West Indies' bubble to attend a funeral on Friday, and has been self-isolating since then in his room on-site. He will watch the squad's second intra-squad warm-up game from his balcony this week, and will be permitted to join back up with the group on Thursday once he has been cleared through the required number of negative Covid-19 tests.
That means that the burden will fall on assistant coaches Roddy Estwick and Rayon Griffith ahead of the four-day, first-class fixture that starts on Monday, with Floyd Reifer helping out as batting coach.
A CWI spokesperson confirmed on Saturday that Simmons was "in self-isolation currently" after the Daily Mail broke the story. In a statement on Sunday evening, CWI said that Simmons had attended a "small private family cremation" for his father-in-law, having sought permission to do so from medical staff before the tour had begun.
"The entire process of his exit and re-entry to the bio-secure location was approved and managed by the medical teams of CWI and the ECB and strictly followed protocols set up prior to the tour which addressed such scenarios," the statement said.
CWI added that Simmons had already taken two Covid-19 tests since returning to Old Trafford, both of which came back negative. Dr. Donovan Bennett, the chairman of CWI's medical advisory commitee, said: "[We are] happy with the feedback we have been receiving from our medical associates in the United Kingdom.
"Phil Simmons adhered to the process of managed exit and re-entry as discussed with and agreed on between CWI and the ECB. These contingencies were put in place before the tour was agreed on and all exits from the bio-secure environment must be agreed by both medical teams, before concessions are given."
Speaking in a virtual press conference on Saturday, Joseph said that Simmons' absence "doesn't really disrupt" West Indies' preparations.
"We have our jobs to do - we have our preparation to keep going with," he said. "We have a very big coaching staff here that are very supportive of each other, so that's not really a problem for anyone."
Joseph, who looks set to form part of a four-man seam attack in the first Test along with Kemar Roach, Shannon Gabriel and Jason Holder, added that he hoped he could use any perception of him as a "weaker link" to his advantage.
"Obviously those three guys have a lot more experience than I do," he said. "I'd think more often than not, teams would see me as the weaker link. I think my job is to come in and just back those bowlers [up] and keep the pressure on.
"It's not necessarily because of age, but because of the number of matches I've played compared to the other three bowlers. I could use it as an advantage - I know my abilities and they [England] might not know. But once I turn up on the day and get the job done, I know I can get on top of any opponent.
"I see this tour as an opportunity for me to help the team to get higher up the rankings. Any opportunity I get to play, I'll take it, and whatever the captain and the team require me to do, I'll put my best foot forward."
Joseph took six wickets in this week's warm-up game, including that of Shai Hope in each innings, and said that he felt as though he was hitting his straps well heading into the series.
"I'm just looking to stay consistent," he said. "I think I bowled pretty well [this week] so I'm just looking to repeat what I did in the last game.
"[The 2017 tour] was a really big learning experience for me, my first time in England. So I have some experience here now - I know how to bowl in these conditions my second time around.
"The ball does a bit more here in England than in the Caribbean. It's just some slight adjustments, nothing too big but some simple adjustments. For me, I think it's about being consistent round that good area, extracting whatever movement you can get off the pitch, and sticking to plans as long as possible."
June 28, 2030 GMT - This story was updated to include Cricket West Indies' statement