The 32-year-old was not part of Madrid's squad for Sunday's 4-0 defeat to fierce rivals Barcelona, which head coach Carlo Ancelotti put down to illness.
Bale has played in just five of Madrid's 42 matches in all competitions this season, totalling 270 minutes on the field – the equivalent of three whole games.
Despite repeated setbacks, the former Tottenham star has played 233 minutes for Wales across four games this season, helping to keep his side's qualifying dreams alive.
And Bale insists he is capable of lasting the distance against Austria, with the winners going on to face either Scotland or the Czech Republic in June's rescheduled final.
"Obviously it's normal to have some [injury] niggles now and again," he said.
"I've been good. I've been training for what, the last two and a half months. I got some minutes maybe three weeks ago or so. So now I'm in very good shape.
"I'm obviously in a lot better shape than I was for the last camp, where I'd been out for about three months. I've been training now over the last couple of days.
"I'm ready to play whatever's necessary. And yeah, we'll give it everything we can."
While Ancelotti implied Bale's most recent absence was down to illness, reports in Spain suggested the forward ruled himself out of contention because of a back strain.
Asked to clarify why he was not part of the squad to face Barcelona, Bale said: "I don't need to. I don't need to tell anyone what was up.
"I don't need to give anyone anything to use against me. Everything is fine now, I have no issue."
Bale earned cap number 100 for Wales in November's win over Belarus and has scored 36 goals and assisted 23 more over that period.
And after representing his country at Euro 2016 and Euro 2020, Bale is now fully focused on leading his side to a first World Cup finals since 1958.
"For sure, the Austria game will be one of biggest I've played in," he said. "Qualifying for a World Cup is something I want to achieve, as do the fans and the country.
"We need to take it in our stride like we always do. Everyone will step up – it's what we do best.
"To get to the World Cup with Wales would be an incredible achievement. We'll fight for our country like we always do."