ATP World Tour Finals
Venue: O2 Arena, London Dates: 21-28 November
Coverage: One match each day live on BBC TV, streamed online & available through iPlayer; text commentary online and on mobiles for every singles match via BBC Sport website; every singles match live on 5live sports extra.
Soderling was forced to fight all the way in a tense second set
By David Ornstein at the O2 Arena
Robin Soderling bounced back from his opening-day defeat by Andy Murray to battle past David Ferrer and keep alive his hopes of reaching the knockout stage at the ATP World Tour Finals.
The world number four survived a late wobble to win 7-5 7-5 and go joint-second in Group B alongside Murray, who lost to Roger Federer in Tuesday's afternoon match.
Soderling needed to win to have any chance of making it out of the round-robin phase, but he could now advance whether or not he beats Federer on Thursday.
With the top two going through to the semi-finals, Federer leads the pool on two wins, from Murray and Soderling on one while Ferrer, who plays Murray on Thursday, is without a win.
As things stand, Murray would qualify alongside Federer because he has a better head-to-head record than Soderling, who he beat in his opening match. The second criteria is percentage of sets won, followed by percentage of games won.
The 26-year-old Swede said: "I served very well, especially in the first set. But it was tough. It was a close match, two really tough sets.
"I'm lucky that I won. I still feel that I have a lot of things that I can improve. Hopefully I can do that in one or two days and play a good match in my next match."
Soderling arrived in London as the man in form following a triumph at the Paris Masters that saw him leapfrog Murray into a career-high ranking of four in the world.
He beat Rafael Nadal and Novak Djokovic en route to the semi-finals on his end-of-season championships debut last year, while five of his six career ATP World Tour titles were won indoors.
But a resounding defeat by Murray on Sunday, allied to Federer's victory over the Scot, meant Soderling was staring at the prospect of an early exit.
Ferrer may be the least-heralded of the eight-strong field but he reached the final on his only previous appearance in 2007 and ousted Soderling on his way to the Valencia Open title at the start of November.
That triumph was secured on a surface similar to the one in use at the O2 and, although Ferrer was soundly beaten by Federer on Sunday, the diminutive right-hander knew victory would seal a winner-takes-all meeting with Murray on Thursday.
I tried to do my best. I fought to win the second set, but Robin played better than me and he had more chances all the match
Soderling got proceedings under way with a morale-boosting service hold in which his delivery already looked to be functioning better than it had two days previously.
Pre-tournament statistics suggested Ferrer was one of the weaker servers in the eight-man field and it was an area Soderling seemed to target from the outset.
The Spaniard managed to hold firm in games two and four but Soderling attacked with greater purpose in game six and Ferrer was forced to stave off two break points.
The ferocity of Soderling's groundstrokes were drawing occasional gasps from the near-capacity crowd and, at times, Ferrer too was reduced to the role of a spectator.
He collected just four points from Soderling's opening six service games and then found himself under huge pressure when serving to stay in the first set at 5-6.
Soderling bludgeoned his way to 15-40 and two set points only to squander them both. A third went begging when an off forehand sailed narrowly wide, but at the fourth time of asking the Swede passed Ferrer with a majestic forehand.
There was more resolve about Ferrer - nicknamed 'The Wall' - at the start of the second set and after staving off another break point in game two, he got to 0-30 on the Soderling serve.
Ferrer staged a late revival but he left himself with too much to do
The number four seed was becoming agitated, repeatedly gesticulating to his support team in the stands, but he retained sufficient composure to avert the danger and transfer the pressure back on to Ferrer's shoulders.
Ferrer was initially up to the challenge and continued to play to more aesthetically-pleasing tennis to keep himself in contention.
An increasingly-emotional Soderling cranked up the intensity once more in game six and broke with a volley into open court before holding serve for 5-2.
This was a stunning show of power tennis from the 26-year-old and it felt like he would cruise over the line, but Ferrer had other ideas and dipped into his renowned energy reserves to break back in game eight and square the set at 5-5.
The momentum was with now with the 28-year-old and, sensing a deciding set, the crowd came to life.
Unfortunately for them, Soderling restored his control and held for 6-5 before breaking in game 12 to secure the one hour and 41-minute win.
However, it remains to be seen how costly the concession of those two late games will prove for the Swede.
Ferrer conceded his opponent had been superior on the night in London and said: "I tried to do my best. I fought to win the second set, but Robin played better than me and he had more chances all the match.
"I didn't have any chances in the match. Maybe in the second set at 5-5, 15 30 but he served really well all match. I think the surface is similar to Valencia. I won in Valencia. I didn't have any problems, it was just Robin's serve was really good and he took more chances on my serve."