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Which of the following is grammatically correct?

Even if ____, I probably won't be able to ____.

Could it be rephrased this way and still remain grammatically correct?

Even if ____, I probably can't _____.

Is there a difference?

How about this?

Even if I find the keys, I probably can't start the car.

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possible duplicate of "will be able to" vs. "can" – kiamlaluno Jun 30 '11 at 23:33
I really have no idea what you are trying to ask. Are you asking if won't be able to and can't are interchangeable? Are you asking if all possible forms of your examples are grammatically correct? – MrHen Jul 1 '11 at 0:46
@MrHen: The 'keys' question is dealt with per kiamlaluno's comment, whether OP was aware of the earlier question or not. That still leaves the two different usages of Even if... which OP presents and asks us to consider. – FumbleFingers Jul 1 '11 at 1:28
@Fumble: If that is the question being asked here, I highly suggest some editing be done to make it a little more accessible. – MrHen Jul 1 '11 at 1:59
@MrHen: Good point. But I'd rather wait to see if OP will clarify his own thoughts before imposing my interpretation on it. Though if he doesn't see it my way, I guess I'll have to vote to close anyway... :) – FumbleFingers Jul 1 '11 at 2:55

As a rule, the first missing element in the first format would be something which really is undecided/unknown at the time...

Even if win the lottery, I probably won't be able to buy Buckingham Palace

In the second sentence, the missing element would normally be something already postulated to be true (by the speaker, but not necessarily accepted as such by the person being addressed)...

Even if I am stronger than you, I probably can't beat you in a boxing ring

In that second sentence, even if really means even though. It's a common way of phrasing such statements.

Per kiamlaluno's comment, the difference between can't and won't be able to is covered elsewhere. This answer addresses the different meanings of Even if... But to answer OP's question as posed, the sentence is non-standard. It should be...

Even if I find the keys, I probably won't be able to start the car

...because the underlying form is that of my first example.

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What about "Even if I find the keys, I probably can't start the car." – language hacker Jun 30 '11 at 23:31
@language hacker: That would be at the very least 'non-standard'. The normal form would be ...probably won't be able to start the car. – FumbleFingers Jun 30 '11 at 23:38

The two terms are roughly synonymous. "I can not" implies impossibility on its face. "I will not" implies an unwillingness, or more figuratively a statement of present and future certainty. Combined with the infinitive "be able to" implying a state of possibility, the term implies you are certain of the impossibility.

The only possible difference would be that "can't" may imply that you know by experience, or have proven, that the task is impossible for you, where "won't be able to" is an untested but highly confident hypothesis of the impossibility.

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Well, you can rephrase it and it will remain grammatically correct, but the meaning will change dramatically, because won't be able to talks about a future event, while can't talks about a present event.

For further information see my (accepted) answer to “will be able to” vs. “can”.

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So if I say Andy Murray can't win at Wimbledon in a few days, is that bad grammar, or just a bad attitude? – FumbleFingers Jul 1 '11 at 1:22
It's a correct grammar, of course, because the specific time is defined by "at Wimbledon in a few days." I don't get it why people do this all the time on this site. I was answering to OP's concrete sentences. I don't think he wanted a dictionary with all the possible meanings and usage there is. Oh well, whatever ... – RiMMER Jul 1 '11 at 9:50
I didn't mean to sound unduly critical. Just a bit of a topical joke really, reacting to your can't talks about a present event. Sorry if it fell flat. He lost anyway, so at least I was right about that even if I didn't want to be. :) – FumbleFingers Jul 1 '11 at 20:41

Fundamentally, I'm not sure what you're highlighting is anything terribly special about "can". Just as with "will + infinitive" vs the persent tense in general, using "will" tends to imply that you are realising/making up/refining your reasoning as you speak, whereas the present tense (and in this case "can") implies that you had already decided on the future action. It's a slightly subtle difference and there are surely cases where the two could be used more or less interchangeably.

Oh, and of course "can" can refer to a present/ongoing truth, but I guess that wasn't the case that you were unsure about.

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