By Piers Newbery
BBC Sport at Wimbledon
Serena Williams admitted she was impressed by the fighting qualities shown by her sister Venus in Saturday's Wimbledon final.
The world number one retained her title with a three-set victory but the match was overshadowed by injuries to her elder sister.
Venus picked up an abdominal injury last month and was also suffering from a hip problem that cut her morning practice session to just 15 minutes.
She needed a treatment break of several minutes in the third set of the final but insisted on playing out the match.
"She's tougher than I ever thought she was," said Serena.
"I knew she was tough but she's gone on to a whole different level. To play today knowing she was injured, she's definitely up there with the real fighters and champions."
Serena revealed that the sisters had not discussed Venus' injury situation before the match and there had been no threat of her defaulting.
And the champion admitted that she looked to exploit the injury whenever Venus approached the net.
I couldn't run too fast, I couldn't stretch out too much and I was hitting serves in the net because it's harder to reach up
Defeated finalist Venus Williams
"I was just telling myself this is Wimbledon and I may not get this opportunity again. If anything that made me fight harder and kept me motivated.
"When she came to the net I hit the lob instead of a passing shot but I was really fighting, and she was too."
Serena was left alone on court during the injury break but insisted she had not let her mind wander to feeling sympathy for her sister.
"I was going to serve next and I wanted to make sure that I was ready," said Serena
"I thought she'd come back tougher because I knew she was going to get the injury re-taped and the pain would be relieved."
Venus received treatment during the final set
Venus revealed that her decision to play the final was made partly as a reaction to past criticism that the sisters default too easily.
"Serena and I have taken a lot of slack and I thought I'd take one for the team," she said.
"We've been blamed for a lot of things that never even happened so I felt today I should play. I had to at least show up and go out on the court.
"But if it wasn't the Wimbledon final the chances of me playing probably would have gone down."
And the former champion admitted she had been severely hampered during the match.
"I couldn't run too fast, I couldn't stretch out too much and I was hitting serves in the net because it's harder to reach up. But Serena played really well."