The Blues face a run of nine games over the next 19 days and the squad will be pushed to the limit in their quests to win both the FA Cup and Europa League, while also securing a top-four finish.
Terry will undoubtedly be instrumental to the cause and, having retired from England duty, the captain has been able to concentrate his efforts over the international break on regaining his fitness.
The 32-year-old has been unable to cement a spot in the centre of defence, with David Luiz, Branislav Ivanovic and Gary Cahill often preferred, but Benitez believes Terry's injury, suffered during an accidental clash with Luis Suarez during a 1-1 draw with Liverpool in November, is finally healing.
The Spaniard told reporters: "He has been training with us and we are really pleased with his condition. He’s training every day and improving his fitness.
|7/2||Chelsea are 7/2 to win the FA Cup with Bet365|
Chelsea's fixture pile-up begins this weekend as they face two games within 45 hours of each other with a trip to Southampton in the league on Saturday being followed by an FA Cup replay against Manchester United at lunchtime on Easter Monday.
Benitez feels two games in three days will test Terry to the limit but says the hectic schedule is not a problem for the club.
He revealed: "It is better to have this problem than be at home watching the TV.
"Having a busy schedule means you are progressing and competing. It’s true that this will be the defining period of our season.
"In a top side the last 10 games and the last month is when you fight for trophies. We’re still in there, which is a positive. At this stage you have to win to win trophies. The spirit has to be there now, not in September."
While most of the fans' focus will inevitably turn to the quarter-final with Sir Alex Ferguson's men in four days' time, Benitez has urged his players not to get distracted and deal with the task in hand as they take on a Saints side buoyed by their 3-1 win over Liverpool last time out.
He added: "Hopefully, it is not hard for us because we want to finish in the top two, three or four.
"That is the key for us for the new season. They want to finish in the top four and guarantee Champions League football.
"Hopefully that will be enough motivation. We have to ensure we have competitive teams versus Southampton, Manchester United and Rubin Kazan on Thursday.
"We have to balance the squad and finding the balance is the most difficult thing because the games are so close."