Aston Villa will be without striker Wesley and goalkeeper Tom Heaton for the rest of the season after both suffered knee ligament damage in Wednesday's 2-1 win at Burnley.
Brazil international Wesley, 23, scored the opener but was hurt in a tackle with Clarets' defender Ben Mee.
Former Burnley keeper Heaton, 33, was hurt as he attempted to stop Chris Wood's 80th-minute consolation.
Both players had scans on Thursday and are set for six to nine months out.
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"They are two key players who I feel very sorry for," said Villa boss Dean Smith. "We've had five games in 16 days and another seven to come in January.
"We can't feel sorry for ourselves; we have to deal with it, help the players in their recovery and go and recruit wisely."
Villa officials were unhappy with Mee for the tackle on Wesley - signed from Club Bruges in June for £22m - although the 30-year-old was not ruled by referee Michael Oliver to have committed a foul in the incident.
Heaton has missed just one of Villa's 21 league games this season, while Wesley has started them all, scoring five goals and assisting one.
His goal in the 27th minute on Wednesday was his first in 13 league appearances, having previously scored four in six matches.
Villa are 17th in the Premier League table, one place and one point above the relegation places. Last season's player of the year John McGinn was ruled out until March with a broken ankle suffered in December.
'Grealish not for sale'
Speaking about the January transfer window, Villa boss Smith he would be holding transfer talks with chief executive Christian Purslow and sporting director Jesus Garcia Pitarch.
"We've got business planned; that'll continue," Smith said. "I'm sitting down tonight with Christian and Jesus to see what this changes for us.
"It'll hasten what we do in the market. The recruitment side won't change from what we were looking at before."
Smith also said midfielder Jack Grealish, who has six goals and five assists in the Premier League this season, was not for sale.
"He's a big target for many teams," said Smith. "Our owners are very ambitious in establishing us as a top Premier League club; to do that you need to keep your best players.
"People can keep looking but they can't touch. We want to keep our best players and he's showing he's one of the best in the Premier League."