As of Sunday, Collins said there are no indicators of how long it will take for Bay to return, and that the left fielder was scheduled to simply rest over the weekend.
Bay signed a four-year, $66 million deal with the Mets before the 2010 season, and he has struggled during his time in New York. Collins said he thought Bay had turned a corner at the end of the '11 season, and that this injury is just the latest installment of what has been an unlucky tenure in New York.
"At the end of last year, he started to look like he was enjoying himself here, having more fun," Collins said. "He came into Spring Training with a tremendous attitude. I thought this was going to be the year that he breaks out. He's just been unable to keep himself on the field due to the way he plays -- which is max effort all the time.
"I will always [believe] that he put way too much pressure on himself to try and live up to all of the expectations there were here instead of just going out and playing and enjoy playing," he continued. "When he came here he wanted to be the guy that everybody could turn to, and what he was was a very, very good player. I feel terrible for him and terrible [about] his injuries."
Collins said that Bay's aggressive play has been the cause of his injury-plagued seasons with the Mets, but admitted that there was no way to prevent him from making those types of plays.
"I don't think the personality of guys can change like that," Collins said. "They're going to continue to play because they react. It's like anything else, those instincts that they have are, 'Hey, I can catch that ball, but I've got to dive for it.' And they do it, they don't think about their health."
The Mets' skipper said he hopes to get Bay back in the lineup as soon as possible, but is extremely concerned about the severity of the concussion. Though the disabled list for concussions is only seven days, Collins said he is unsure about the timetable for Bay's return, but understands all precautionary measures taken.
"The trainers are so much more educated than they were 25 years ago," he said. "The doctors are seeing the ramifications of letting guys come back in and [how dangerous it is]. I think the knowledge has improved, the treatment has improved, and I'm on board for it.
"Years ago, guys didn't make the kind of money they make today. You had to survive. If you didn't play, someone else took your job. It's not like that today, so I certainly support how they go about it."
Though Bay's career isn't necessarily hanging in the balance, Collins admitted that the recurring injuries may be taking a toll on the 33-year-old, who is also a father of three. He stressed the importance of Bay's presence in the clubhouse and his desire to see him return to the lineup, but acknowledged that the decision was ultimately out of his hands.
"I know Jason Bay is a very, very sharp guy," Collins said, "and he'll make the decision that's best for him and his family."