According to David Hytner of the Guardian, the right-back has suffered a ruptured cruciate knee ligament and is set to be sidelined for the next six months. As such, his main aim is now likely to be getting fit for the start of the 2019-20 term.
"Bellerin will seek further medical opinions over the coming days which will help to place an exact time frame on his absence," the report continued. "But a cruciate rupture normally involves a minimum of six months out."
Speaking after the match on Saturday at the Emirates Stadium, which Arsenal won 2-0 against their London rivals, manager Unai Emery confirmed he was "not positive" about the injury accrued by the Spain international, per BBC Sport.
Prior to the issue that saw him stretchered off the field, Bellerin had been having a positive impact on the game, providing an assist for the opening goal scored by Alexandre Lacazette:
Scouted Football @ScoutedFtbl
🔴 Héctor Bellerín (23) vs Chelsea: 59 touches 31/38 passes 3/4 long balls 3 interceptions 3 clearances 2/3 aerial duels 2/2 dribbles 2/2 tackles 1/1 crosses 1 key pass 1 assist Crucial under Unai Emery; performances like yesterday are the reason why he will be such a big miss. https://t.co/5y6eXNQGP6
The injury is a huge blow to the player, especially given the start against Chelsea was his first for five weeks; he'd been recovering from a calf issue.
Bellerin is capable of transforming Arsenal when he is in the side. The 23-year-old's raids down the right flank have become trademark, with his searing speed and limitless energy making him a tough player to contain at full flight.
Emery will now have to find a solution to the right side of his defence for the remainder of the campaign, although it's clear the team will be worse off without one of the Premier League's best right-backs to call upon.
James McNicholas of Gunnerblog thinks the best option for the manager may be to give Ainsley Maitland-Niles a run in the side:
If, as looks likely, Bellerin is out for a good while, I'd be inclined to give Maitland-Niles the chance at right-back. He might envisage himself playing a different position, but this is a great opportunity for him - and he does have a lot of the tools. Could save us some cash.
The other alternative in the position is veteran Stephan Lichtsteiner, who was drafted in on a free transfer in the summer to cover the full-back areas. However, he's been found out against dynamic wingers at various points this season.
Given there is still time left in the January transfer window, the Gunners could yet make a signing in the position, although this long-term injury may have caught them off guard.
As such, they're likely to be left short, meaning progressing in the FA Cup and UEFA Europa League, as well as challenging for a top-four spot in the Premier League—they sit in fifth as things stand, three points behind Chelsea in fourth—suddenly looks a lot harder.