By Bruce Levine–

CHICAGO (CBS) — It surely hasn’t been shortstop Starlin Castro’s fault that the Chicago Cubs have been an awful team in the first four years of his career. The longest consecutive tenured Cub in service time, Castro has matured on and off the field since arriving on May 7, 2010.

READ MORE: Kenosha County Sheriff's Deputy Shoots Chicago Homicide Suspect At Bristol Gas Station After Two-State Crime Spree; Suspect Shot Police K-9 During Confrontation

The fact that he has never played on a team that was over .500 in the standings isn’t a reflection of his ability and skill set. That said, the assumption by most is he won’t be a Cub forever.

Despite Castro being named to three All-Star teams and playing 98 percent of the Cubs games when not on the disabled list, some outsiders seem unsatisfied with his play. Castro has been singled out by some in the media and around the fan base as not quite being up to the standard they want from a big league shortstop.

Until recently, his offense in 2015 had been without impact. That changed over the weekend series against Cincinnati. Castro had back-to-back walk-off hits Saturday and Sunday. His three-run home run Friday also got the Cubs back into a tie late in that game. His .265 batting average and 13 errors in the field have many observers pointing toward a trade of the 25-year-old Dominican Republic native.

Castro is signed through 2019 with a club option for 2020. His seven-year, $60-million deal is really small potatoes for a player who plays every game with energy and is nowhere near his peak as a potential offensive force.

The ascension of Addison Russell to the major leagues have murmurers saying that the athletic second baseman will soon be the Cubs’ best alternative at shortstop. And Russell may well be the Cubs’ shortstop of the future. That said, Castro isn’t about to flinch if he has to move on.

I asked Castro if he is content with his game at this point.

“I am really happy because our team is very, very good,” he said. “I still think I can do more than I have. My job is to prepare and do what I can to help the team win a game.”

The maturity factor for Castro has been helped by the addition of better players. The past two seasons, Castro and Anthony Rizzo had to do all of the heavy lifting on the field and as leaders in the clubhouse. This was asking way too much from two 24-year-old players.

READ MORE: Man, Woman Robbed At Gunpoint In Bucktown

“It’s really great for us to have this support,” he said about the addition of a higher-caliber of players to the Cubs. “It is really important now that we have nine guys in the lineup who we trust and support. Now if we get people on base and they don’t want to pitch to me, I can take my walk. I can trust the guy behind me to get it done. That is the type of (situation) you want to win.”

Castro hasn’t been happy about making errors on plays that have been basically routine grounders slightly to his right. He has been working with infield instructor Gary Jones on his pre-pitch set-up in the field. The Cubs have moved him a little deeper back on the dirt and have Castro taking a couple of small steps toward the batter before the pitch.

“This has been a problem that I have been working on,” Castro said. “The problem is I am making errors because I am staying back on the ball. If you let the ball travel, something bad can happen. I am trying to attack every ball.”

The trade rumors have been unfounded for Castro so far. Certainly conversations about players take place with teams every day, and the Mets and Phillies have been the two teams most closely associated with Castro’s name. But a source confirmed last week that Castro wasn’t on the Phillies’ radar. The Mets have plenty of young pitching but haven’t been aggressive in the trade market as of yet.

For now, the Cubs’ main focus isn’t trading Castro. Do they think that Russell could handle the position at this level? They aren’t saying, but the presumption is yes.

For his part, manager Joe Maddon is happy with Castro’s work habits.

“He is getting better,” Maddon said Monday. “He really works so hard. His work has been great. He hit at a very high level in the past, which tells me he will do it again. We also talked about the fact he has been trying a little bit too hard sometimes. That is where that roll-over ground ball comes from. I always tell him I want left center to be his left-field foul line. We want him to not try and pull the ball so much. The defense is about messing up the routine play, but how about the relay last night.”

Castro is a Cub for now, and his game should get better. What team he plays for in the future and at what position he plays, your guess is as good as mine.

MORE NEWS: Chicago Weather: Temperature Drop Friday Morning

Bruce Levine covers the Cubs and White Sox for 670 The Score and CBSChicago.com. Follow him on Twitter @MLBBruceLevine.